阅读说明：本技术 光波导芯片的连接结构 (Connection structure of optical waveguide chip ) 是由 鹿间光太 石川裕士 河尻祐子 荒武淳 于 2018-06-07 设计创作，主要内容包括：一种光波导芯片的连接结构包括：基底(2003),凹槽(2013)形成在基底中；间隔光纤(2006),每个间隔光纤针对凹槽(2013)中的对应一个来设置并装配在凹槽(2013)中,同时从基底(2003)部分地突出；以及石英基PLC(2001、2002),其为多个光波导芯片,其装配在间隔光纤(2006)的突出部分上的凹槽(2007)中的每一个形成在光波导层(2008)的面对凹槽(2013)的位置处,并且石英基PLC(2001、2002)中的每一个安装在基底(2003)上,同时被间隔光纤(2006)支撑。石英基PLC(2001、2002)安装在基底(2003)上,使得光波导层(2008)的入射/出射端面彼此面对。(A connection structure of optical waveguide chips includes a substrate (2003) in which grooves (2013) are formed, spacer fibers (2006) each provided for a corresponding of the grooves (2013) and fitted in the grooves (2013) while partially protruding from the substrate (2003), and quartz-based PLCs (2001, 2002) which are a plurality of optical waveguide chips each of which fitted in grooves (2007) on protruding portions of the spacer fibers (2006) is formed at a position facing the grooves (2013) of an optical waveguide layer (2008), and each of the quartz-based PLCs (2001, 2002) are mounted on the substrate (2003) while being supported by the spacer fibers (2006). the quartz-based PLCs (2001, 2002) are mounted on the substrate (2003) such that incident/exit end faces of the optical waveguide layer (2008) face each other.)

1, A connection structure of optical waveguide chip, comprising:

a substrate in which a plurality of th grooves are formed;

a plurality of th spacing members fitted in the plurality of th grooves, respectively, while partially protruding from the base, and

a plurality of optical waveguide chips in each of which an optical waveguide layer is formed on a substrate and second grooves fitted on protruding portions of the th spacing member are formed at positions of the optical waveguide layer facing the th grooves, and each of which is mounted on the substrate while being supported by the th spacing member,

wherein the plurality of optical waveguide chips are mounted on the substrate such that the incident/exit end faces of the optical waveguide layers of two adjacent optical waveguide chips face each other.

2. The connecting structure of an optical waveguide chip according to claim 1,

each of the optical waveguide chips includes at least two second grooves formed in a surface of the optical waveguide layer facing the substrate such that , which is a direction of an optical axis of light entering from an adjacent another optical waveguide chip and an optical axis of light exiting to the another optical waveguide chip, is a longitudinal direction, and

the substrate includes at least two th grooves, the at least two th grooves being formed in a surface facing the plurality of optical waveguide chips such that the at least two th grooves correspond to the at least two second grooves, respectively.

3. The connecting structure of an optical waveguide chip according to claim 1 or 2, wherein the second groove formed in the optical waveguide layer of the optical waveguide chip is formed to a depth that exposes a substrate of the optical waveguide chip, and the th spacing member fitted in the second groove is in contact with the substrate of the optical waveguide chip.

4. The connecting structure of optical waveguide chip of any of claims 1 to 3, wherein the height of the th spacing member is higher than the sum of the depth of the th groove and the depth of the second groove.

5. The connecting structure of optical waveguide chips according to claim 2, wherein each optical waveguide chip further comprises at least third grooves, the at least third grooves being formed in a surface of the optical waveguide layer facing the substrate such that of a direction perpendicular to an optical axis direction of light entering from the other optical waveguide chip and a direction perpendicular to an optical axis direction of light exiting to the other optical waveguide chip is a longitudinal direction,

the substrate further comprising at least fourth grooves, the at least fourth grooves being formed in a surface facing the plurality of optical waveguide chips to correspond to the at least third grooves,

the connection structure further includes at least second spacing members, the at least second spacing members being fitted in the fourth groove while partially protruding from the substrate, wherein a portion protruding from the substrate is fitted in the third groove, and

the length of the th and second grooves in the optical axis direction is longer than the length of the th spacing member in the optical axis direction, and

the third groove and the fourth groove have a width in the optical axis direction wider than a width of the second spacing member in the optical axis direction.

6. The connecting structure of an optical waveguide chip according to claim 5, wherein the second groove and the third groove formed in the optical waveguide layer of the optical waveguide chip are formed to a depth that exposes a substrate of the optical waveguide chip, and the th and second spacing members fitted in the second and third grooves, respectively, are in contact with the substrate of the optical waveguide chip.

7. The connecting structure of an optical waveguide chip according to claim 5 or 6, wherein the th groove and the fourth groove formed in the substrate have the same depth, and the second groove and the third groove formed in the optical waveguide chip have the same depth, and

the th spacing member and the second spacing member have the same height, and the th spacing member and the second spacing member have a height that is greater than the sum of the depths of the th groove and the fourth groove and the depths of the second groove and the third groove.

8. The connecting structure of optical waveguide chips of any of claims 1 to 7, wherein each optical waveguide chip further comprises a spot-size converter configured to increase a mode diameter of the optical waveguide in the vicinity of a connecting end face facing another adjacent optical waveguide chip.

9. The connecting structure of optical waveguide chips according to claim 1, wherein each of two adjacent optical waveguide chips further include a pitch converting portion configured to make a spacing between cores in an incident/exit end face of an optical waveguide array formed in the optical waveguide layer narrower than a spacing between cores in a portion away from the incident/exit end face.

10. The connecting structure of optical waveguide chips as claimed in claim 9, wherein each of the optical waveguide chips has a shape having cutouts in at least of corner portions of the incident/exit end face facing another adjacent optical waveguide chips.

11. The connection structure of an optical waveguide chip according to claim 9 or 10,

each of the optical waveguide chips includes at least two second grooves formed in a surface of the optical waveguide layer facing the substrate such that of an optical axis direction of light entering from an adjacent other optical waveguide chip and an optical axis direction of light exiting to the other optical waveguide chip is a longitudinal direction,

the substrate includes at least two th grooves, the at least two th grooves being formed in a surface facing the plurality of optical waveguide chips such that the at least two th grooves correspond to the at least two second grooves, respectively, and

each of the th and second grooves fit over the th spacing member at a central portion, and as a point is spaced apart from the central portion in the longitudinal direction, the width becomes wider than the th spacing member.

12. The connecting structure of an optical waveguide chip according to claim 11, wherein a planar shape of each of both side ends of the th groove and the second groove in a longitudinal direction is a shape in which a distance from a groove center is substantially constant and a distance between the both side ends is set so that the both side ends of the th groove and the second groove are in contact with both side ends of the th spacing member in a longitudinal direction when fitted on the th spacing member.

13. The connection structure of optical waveguide chips of claim 1, wherein the substrate comprises the th grooves formed in a surface of a cladding layer facing the plurality of optical waveguide chips, and further comprises at least third grooves formed in the surface of the cladding layer.

14, A connecting structure of optical waveguide chip, comprising:

an th optical waveguide chip, wherein a th optical waveguide layer is formed on a th substrate, and a plurality of th grooves are formed in the th optical waveguide layer;

a plurality of spacing members respectively fitted in the plurality of th grooves while partially protruding from the th optical waveguide chip, and

a plurality of second optical waveguide chips, in each of which a second optical waveguide layer is formed on a second substrate and second grooves fitted on protruding portions of the spacing member are formed in a surface of a cladding layer of the second optical waveguide layer facing the -th groove, and each of which is mounted on the -th optical waveguide chip while being supported by the spacing member,

wherein the plurality of second optical waveguide chips are mounted on the th optical waveguide chip such that the incident/exit end faces of the second optical waveguide layers of two adjacent second optical waveguide chips face each other, and

each of the second optical waveguide chips includes at least third grooves, the at least third grooves being formed in a surface of the cladding layer facing the th optical waveguide chip.

15. The connecting structure of an optical waveguide chip according to claim 13 or 14, further comprising a filling material filling the third groove,

wherein the filling material is made of a substance having a thermal expansion coefficient different from that of the clad layer in which the third groove is formed.

16. The connecting structure of an optical waveguide chip according to any one of claims 13 to 15, wherein the third groove is formed to a depth at which a substrate is exposed through the cladding layer in which the third groove is formed.

17. The connecting structure of an optical waveguide chip according to claim 13, wherein each of the optical waveguide chips include the second groove in a surface of the cladding layer of the optical waveguide layer facing the substrate, and further include at least fourth grooves formed in the surface of the cladding layer.

18. The connecting structure of optical waveguide chips as claimed in claim 14, wherein the th optical waveguide chip further comprises at least fourth grooves formed in a surface of the cladding layer of the th optical waveguide layer facing the plurality of second optical waveguide chips.

19. The connecting structure of an optical waveguide chip according to claim 17 or 18, further comprising a filling material filling the fourth groove,

wherein the filling material is made of a substance having a thermal expansion coefficient different from that of the clad layer in which the fourth groove is formed.

20. The connecting structure of an optical waveguide chip according to , wherein the fourth groove is formed to a depth at which a substrate is exposed through the cladding layer in which the fourth groove is formed.

21. The connection structure of an optical waveguide chip according to claim 15 or 19, wherein the filler is made of which is a substance having a hardness lower than that of the clad layer around the filler and a substance having a thermal expansion coefficient higher than that of the clad layer around the filler.

22. The connecting structure of optical waveguide chips of claim 1, further comprising at least pressure mechanisms, the at least pressure mechanisms being configured to press the plurality of optical waveguide chips in the direction of the substrate,

wherein the pressure mechanism is disposed on the substrate of the optical waveguide chip.

23. The connecting structure of an optical waveguide chip according to claim 22, wherein the pressing mechanism is arranged such that a pressing position is a gravity center position of the optical waveguide chip.

24. The connecting structure of an optical waveguide chip according to claim 22, wherein the pressing mechanism is arranged such that a pressing position is a position near a connecting end face of the optical waveguide chip.

25. The connecting structure of an optical waveguide chip according to claim 22, wherein the pressing mechanism is arranged such that a pressing position is a position directly above the second groove and the th spacing member of the optical waveguide chip.

26. The connection structure of an optical waveguide chip according to , wherein the pressure mechanism includes of a mechanism configured to press the optical waveguide chip by a weight of the mechanism, a mechanism configured to press the optical waveguide chip by a bolt advanced while being in threaded engagement with a fixing member configured to hold the pressure mechanism, and a mechanism configured to press the optical waveguide chip by a restoring force of a spring.

27. The connecting structure of an optical waveguide chip according to claim 22, wherein the pressure mechanism comprises:

a plurality of th pressing members, each of the plurality of th pressing members being made of an elastic resin and arranged such that a pressing position is a position directly above the second groove and the th spacing member of the optical waveguide chip, and

a second pressing member provided for each of the optical waveguide chips to press the plurality of th pressing members.

28. The connection structure of an optical waveguide chip according to claim 27, wherein the second pressing member includes of a structure configured to press the th pressing member by a weight of the structure, a structure configured to press the th pressing member by a bolt advanced while being screw-engaged with a fixing member configured to hold the pressure mechanism, and a structure configured to press the th pressing member by a restoring force of a spring.

29. The connecting structure of an optical waveguide chip according to any one of claims 22 to 28, wherein the pressure mechanism is integrated with a holding mechanism configured to hold the substrate, and an alignment mechanism configured to align a mounting position of the optical waveguide chip with respect to the substrate.

Technical Field

The present invention relates to a connection structure of an optical waveguide chip used in a technical field requiring optical signal processing such as optical communication or optical sensing.

Background

In an optical circuit used as an optical communication device, generally uses a Planar Lightwave Circuit (PLC) using a silica glass-based material, since the coupling of the PLC to an optical fiber is excellent and is also reliable as a material, the PLC is applied to various functional elements for optical communication such as an optical splitter, a wavelength multiplexer/demultiplexer, an optical switch, and a polarization control element.

In recent years, in order to cope with the size reduction of the optical circuit described above, research on an optical circuit with a high refractive index difference has been advanced, in which the refractive index of the core is increased, and the refractive index difference between the core and the clad is increased, thereby designing a small minimum bending radius. Further, in the last decade, silicon photonics technology using quartz-based materials with strong light confinement has progressed using silicon processes required for electronic parts and the like, and optical circuits smaller than glass-based circuits have been realized.

Further, widely uses an optical circuit using a ferroelectric material typified by lithium niobate (N) or the like as an optical modulation element, further, a Periodically Polarized Lithium Niobate (PPLN) element using the same material is used as a wavelength conversion element or an optical amplification element as a light emitting element, a light receiving element, or an optical modulation element, a III-V group semiconductor typified by indium phosphide (InP) and gallium arsenide (GaAs) has been put to practical use as a light emitting element, a light receiving element, or an optical modulation element (such as an optical waveguide integrated laser) formed by combining a light propagation mechanism with these materials has also come into wide use .

The above-described optical function element, optical modulation element, light emitting element, light receiving element, wavelength conversion element, and light amplifying element will be referred to as an optical waveguide chip hereinafter various applications using light, such as an optical communication network, an optical sensor, and a light source for a display, have been made for the optical waveguide chip.

When connecting optical waveguide chips, as disclosed in patent document 1, it is necessary to optimize the positions of the two optical waveguide chips by inputting light to optical waveguide chips using optical fibers, receiving light on the output side of the other optical waveguide chip by optical fibers, large-diameter photodiodes, or the like, and performing active alignment mounting so that the intensity of the output light is maximized.

Accordingly, in performing the above-described active alignment mounting, it is necessary to align the end face positions of optical waveguide chips in six axes (a total of six axes including three axes of X, Y, and Z axes and rotations X, Y, and X around the X, Y, and Z axes), and similarly, the end face positions of another optical waveguide chip also need to be aligned in six axes.

Further, in order to perform active alignment mounting, it is necessary to permanently fix an optical fiber array component or the like on the end face of each optical waveguide chip other than the above-described connection end face. Therefore, there is a great limitation in installation. Even in the case where no optical fiber array is fixed on each optical waveguide chip, alignment of the optical waveguide chips can be performed by active alignment mounting. However, in this case, since it is necessary to temporarily connect the optical fiber to the end face of each optical waveguide chip other than the above-described connection end face by active alignment, an alignment axis is increased for temporary connection, and more cumbersome processing is required.

If the optical waveguide chip can be aligned only in accordance with the mechanical accuracy of the member or the like without using the cumbersome process as described above and without inputting/outputting light, the mounting can be greatly simplified. This method of mounting is known as passive alignment. However, in the passive alignment mounting, it is a great challenge to achieve sub-micron accuracy only in terms of mechanical accuracy, and connection loss becomes large.

Further , as a method of achieving both size reduction and easy stacking in an optical signal processing technique of an optical switch or the like, a method disclosed in patent document 2 has been proposed in the structure disclosed in patent document 2, a structure capable of accurately stacking an optical waveguide chip (quartz-based PLC) using passive mounting can be realized.

Fig. 35A to 35D are schematic diagrams showing a stacked structure of the optical waveguide chip described in patent document 2. Fig. 35A is a perspective view of a stacked structure of optical waveguide chips, fig. 35B is an exploded view of parts of the stacked structure, fig. 35C is a diagram showing a bonding surface of a quartz-based PLC and a quartz-based flat plate, and fig. 35D is a sectional view of the stacked structure taken along an xy plane. In fig. 35A to 35D, a total of four members, that is, a quartz-based PLC 1001 as an optical waveguide chip formed of a quartz-based glass layer including a silicon (Si) substrate and a waveguide layer, a quartz-based PLC 1003 also as an optical waveguide chip, and two spacer fibers 1006 (spacer members) are combined to form a stacked structure. Therefore, for application purposes such as signal processing, when the quartz-based PLC is used as an optical input/output front end, even in two dimensions including the substrate direction, the beam input/output ports for the spatial system can be increased, and larger-scale optical signal processing can be realized.

The stack structure shown in fig. 35A to 35D is intended to output input optical signals 1005A and 1005b input from optical fibers or the like as output optical signals 1004a and 1004b as spatial light beams via the function element-integrated quartz-based PLCs 1001 and 1003. As shown in fig. 35A and 35B, the quartz-based PLC 1001 is mounted on the quartz-based PLC 1003.

As shown in fig. 35D, the quartz-based PLC 1001 has a structure in which an optical waveguide layer 1008 is formed on a Si substrate 1009. The optical waveguide layer 1008 is formed of a cladding layer 1010 and a core 1011, and the cladding layer 1010 is formed of SiO₂As a result, the core 1011 is formed in the cladding 1010. Further, a fitting groove 1007 is formed in the cladding layer 1010.

Similarly, the quartz-based PLC 1003 has a structure in which an optical waveguide layer 1013 is formed on a Si substrate 1012. The optical waveguide layer 1013 is formed of a cladding layer 1015 and a core 1016, and the cladding layer 1015 is formed of SiO₂As a result, the core 1011 is formed in the cladding 1010. In the cladding 1015, a fitting groove 1014 is formed at a position facing the fitting groove 1007 of the quartz-based PLC 1001 when the quartz-based PLC 1001 is mounted on the quartz-based PLC 1003.

As shown in fig. 35B and 35C, the quartz-based PLC 1001 is stacked and fixed on the quartz-based PLC 1003 while placing the spacer fiber 1006 between them, which is fitted in the fitting groove 1014 on the quartz-based PLC 1003 side and the fitting groove 1007 on the quartz-based PLC 1001 side.

With the above-described structure, the relative positions of the output cores of the quartz-based PLC 1001 and the quartz-based PLC 1003 can be accurately aligned by the passive alignment mounting according to only the mechanical accuracy of the members and the like.

However, in the stacked structure disclosed in patent document 2, although the two optical waveguide chips (the quartz-based PLCs 1001 and 1003) can be accurately aligned, easy and accurate end face connection between the optical waveguide chips cannot be achieved by passive alignment mounting.

Disclosure of Invention

Technical problem to be solved by the invention

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide kinds of connection structures of optical waveguide chips, which can easily and accurately realize end-face connection between the optical waveguide chips by passive alignment mounting.

Means for solving the problems

According to the present invention, there are provided kinds of connection structures of optical waveguide chips, including a base in which a plurality of th grooves are formed, a plurality of th partition members respectively fitted in the plurality of th grooves while partially protruding from the base, and a plurality of optical waveguide chips in each of which an optical waveguide layer is formed on a substrate and a second groove fitted on a protruding portion of the th partition member is formed at a position of the optical waveguide layer facing the th groove and each of which are mounted on the base while being supported by the th partition member, wherein the plurality of optical waveguide chips are mounted on the base such that incident/exit end faces of the optical waveguide layers of two adjacent optical waveguide chips face each other.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the end face connection between the optical waveguide chips can be easily and accurately achieved by passive alignment mounting, and a multi-chip device can be easily provided. Further, in the present invention, since it is not necessary to fix the optical waveguide chip to the substrate by an adhesive or the like, pluggable optical connection capable of connecting the necessary optical waveguide chip only when necessary can be realized, and various restrictions in application can be eliminated from the viewpoint of mounting.

Drawings

Fig. 1A to 1D are schematic views showing a connection structure of an optical waveguide chip according to an th embodiment of the present invention;

FIGS. 2A to 2D are schematic views showing another connection structure of an optical waveguide chip according to an th embodiment of the present invention;

fig. 3A to 3D are schematic views showing a connection structure of an optical waveguide chip according to a second embodiment of the present invention;

fig. 4A and 4B are schematic diagrams showing a connection structure of an optical waveguide chip according to a third embodiment of the present invention;

fig. 5A and 5B are schematic views showing a connection structure of an optical waveguide chip according to a fourth embodiment of the present invention;

fig. 6A and 6B are schematic views showing a connection structure between a light emitting element and an optical waveguide according to a fifth embodiment of the present invention;

fig. 7A to 7D are schematic diagrams showing connection structures of optical waveguide chips which are the basis of sixth to ninth embodiments of the present invention;

fig. 8A and 8B are diagrams for explaining a problem of the connection structure of the optical waveguide chip shown in fig. 7A to 7D;

fig. 9A and 9B are schematic views showing a connection structure of an optical waveguide chip according to a sixth embodiment of the present invention;

fig. 10A and 10B are schematic views showing a connection structure of an optical waveguide chip according to a seventh embodiment of the present invention;

fig. 11 is a plan view showing another example of a pitch conversion section of an optical waveguide chip according to a seventh embodiment of the present invention;

fig. 12 is a plan view showing another connection structure of an optical waveguide chip according to a seventh embodiment of the present invention;

fig. 13 is a plan view showing a connection structure of an optical waveguide chip according to an eighth embodiment of the present invention;

fig. 14A and 14B are plan views showing the shapes of the fitting grooves of the optical waveguide chip and the quartz-based substrate according to the eighth embodiment of the present invention;

fig. 15A and 15B are plan views showing the shapes of the fitting grooves of the optical waveguide chip and the quartz-based substrate according to the ninth embodiment of the present invention;

fig. 16A to 16D are schematic views showing a connection structure of an optical waveguide chip according to a tenth embodiment of the present invention;

fig. 17A to 17D are schematic views showing a connection structure of an optical waveguide chip according to a tenth embodiment of the present invention;

fig. 18 is a sectional view showing a connection structure of an optical waveguide chip according to a twelfth embodiment of the invention;

fig. 19A to 19D are schematic views showing a connection structure of an optical waveguide chip according to a thirteenth embodiment of the present invention;

fig. 20 is a sectional view showing the structure of a portion in which an optical waveguide layer is divided according to a thirteenth embodiment of the present invention;

fig. 21A to 21D are schematic views showing a connection structure of an optical waveguide chip according to a fourteenth embodiment of the present invention;

fig. 22A to 22D are schematic views showing a connection structure of an optical waveguide chip according to a fifteenth embodiment of the present invention;

fig. 23 is a perspective view showing a connection structure of an optical waveguide chip according to a sixteenth embodiment of the present invention;

fig. 24A and 24B are sectional views showing the connection structure of the optical waveguide chip before and after the provision of the pressure mechanism according to the sixteenth embodiment of the present invention;

fig. 25A and 25B are sectional views for explaining the effect of the sixteenth embodiment of the present invention;

fig. 26A and 26B are schematic diagrams showing another example of a pressure mechanism according to a sixteenth embodiment of the invention;

fig. 27 is a perspective view showing a connection structure of an optical waveguide chip according to a seventeenth embodiment of the present invention;

fig. 28A and 28B are sectional views showing a connecting structure of an optical waveguide chip before and after a pressure mechanism is provided according to a seventeenth embodiment of the present invention;

fig. 29A and 29B are a perspective view and a sectional view showing another example of a pressure mechanism according to a seventeenth embodiment of the invention;

fig. 30 is a perspective view showing a connection structure of an optical waveguide chip according to an eighteenth embodiment of the present invention;

fig. 31 is a sectional view showing a connection structure of an optical waveguide chip after a pressure mechanism is provided according to an eighteenth embodiment of the invention;

fig. 32 is a side view showing a connection structure of an optical waveguide chip according to a nineteenth embodiment of the invention;

fig. 33A and 33B are a plan view of a pressing mechanism according to a nineteenth embodiment of the invention and a diagram showing the bonding surfaces of an optical waveguide chip and a substrate, respectively;

fig. 34 is a sectional view showing a connection structure of an optical waveguide chip after a pressure mechanism is provided according to a nineteenth embodiment of the invention; and

fig. 35A to 35D are schematic diagrams illustrating a conventional stacked structure of an optical waveguide chip.

Detailed Description

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[ example ]

Fig. 1A to 1D are schematic views showing a connection structure of an optical waveguide chip according to a th embodiment of the present invention, fig. 1A is a perspective view of the connection structure of the optical waveguide chip, fig. 1B is an exploded view of parts of the connection structure, fig. 1C is a diagram showing a bonding surface of the optical waveguide chip and a substrate, and fig. 1D is a sectional view of the connection structure taken along an xy plane.

Note that various functional circuits configured to process signals, such as switches and wavelength multiplexers/demultiplexers, are mounted on the optical waveguide chip as necessary. However, this embodiment does not depend on the circuit arrangement in the optical waveguide chip and the function of the circuit. In practice, an appropriate optical circuit is formed in the optical waveguide chip in an arrangement avoiding a fitting groove to be described later. However, since this embodiment does not depend on the arrangement of the circuit, fig. 1A to 1D show an example including only a linear waveguide, and other circuit arrangements are omitted for the sake of simple description.

In fig. 1A to 1D, a total of seven members, that is, quartz-based PLCs 2001 and 2002, which are two optical waveguide chips each formed of a quartz-based glass layer including a Si substrate and a waveguide layer, a quartz-based substrate 2003 manufactured by the same method as the quartz-based PLCs 2001 and 2002 and not including a waveguide, and four spacer fibers (spacer members) 2006 are combined, thereby forming a connection structure.

The connection structure shown in fig. 1A to 1D is configured to be able to propagate an input optical signal 2005 and output it as an output optical signal 2004 via the quartz-based PLCs 2001 and 2002.

As shown in fig. 1D, the quartz-based PLC2001 has a structure in which an optical waveguide layer 2008 is formed on a Si substrate 2009, the optical waveguide layer 2008 is formed of a cladding layer 2010 and a core 2011, the cladding layer 2010 is made of quartz glass, and the core 2011 is formed in the cladding layer 2010 and is made of quartz glass containing a dopant, further, a fitting groove 2007 is formed in the cladding layer 2010, the structure of the quartz-based PLC2002 is the same as that of the quartz-based PLC2001, fig. 1C shows a joint surface of the optical waveguide layer 2008 (cladding layer 2010) and the quartz-based base 2003 of the quartz-based PLCs 2001 and 2002, it is apparent from fig. 1C that two fitting grooves 2007 are formed in PLCs.

As shown in fig. 1A and 1B, the quartz-based PLC2001 and the quartz-based PLC2002 are arranged side by side such that the connection end faces (entrance/exit end faces) 11 and 12 face each other. Two quartz-based PLCs 2001 and 2002 are mounted on a quartz-based substrate 2003.

A quartz glass layer 2012 made of the same material as the clad layer 2010 of the quartz-based PLCs 2001 and 2002 is formed on the surface of the quartz-based substrate 2003 on which the quartz-based PLCs 2001 and 2002 are mounted. In the quartz glass layer 2012, a fitting groove 2013 is formed at a position facing the fitting groove 2007 of the quartz-based PLCs 2001 and 2002 when the quartz-based PLCs 2001 and 2002 are mounted on the quartz-based substrate 2003, as will be described later.

Fig. 1C shows the interface of the quartz glass layer 2012 with the quartz-based PLCs 2001 and 2002, as described above, since two fitting grooves 2007 are formed in PLCs, a total of four fitting grooves 2013 are formed in the quartz glass layer 2012, that is, two fitting grooves 2013 formed at positions facing the fitting grooves 2007 of the quartz-based PLC2001 and two fitting grooves 2013 formed at positions facing the fitting grooves 2007 of the quartz-based PLC 2002.

To manufacture the connection structure according to this embodiment, the spacer fibers 2006 are respectively fitted in four fitting grooves 2013 formed in the silica glass layer 2012 of the silica-based substrate 2003. Then, the two spacing optical fibers 2006 fitted in the fitting grooves 2013 of the silica glass layer 2012 are fitted in the two fitting grooves 2007 formed in the optical waveguide layer 2008 of the silica-based PLC2001 so that the bonding surface of the silica glass layer 2012 and the bonding surface of the optical waveguide layer 2008 (cladding layer 2010) of the silica-based PLC2001 face each other as shown in fig. 1B, that is, so that the Si substrate 2009 is located on the upper side and the optical waveguide layer 2008 is located on the lower side, thereby mounting the silica-based PLC2001 on the silica-based substrate 2003.

Similarly, the two spacer fibers 2006 fitted in the fitting grooves 2013 of the silica glass layer 2012 are fitted in the two fitting grooves 2007 formed in the optical waveguide layer 2008 of the silica-based PLC2002 so that the bonding surface of the silica glass layer 2012 and the bonding surface of the optical waveguide layer 2008 (cladding layer 2010) of the silica-based PLC2002 face each other, thereby mounting the silica-based PLC2002 on the silica-based substrate 2003.

In this way, the quartz-based PLCs 2001 and 2002 may be mounted on the quartz-based substrate 2003 such that the connection end surface 11 of the quartz-based PLC2001 and the connection end surface 12 of the quartz-based PLC2002 closely face each other, and optical connection between the quartz-based PLC2001 and the quartz-based PLC2002 may be achieved.

As shown in fig. 1A, an input optical signal 2005 that has entered the quartz-based PLC2002 propagates through the optical waveguide layer 2008 of the quartz-based PLC2002 to provide various optical functions integrated in the optical waveguide, then exits the quartz-based PLC2002 and enters the quartz-based PLC2001, propagates through the optical waveguide layer 2008 of the quartz-based PLC2001, and exits the quartz-based PLC2001 as an output optical signal 2004.

In this embodiment, the fitting groove 2007 of the optical waveguide layer 2008 of the quartz-based PLCs 2001 and 2002 is formed to a position reaching the Si substrate 2009 such that the Si substrate 2009 is exposed at the bottom of the fitting groove 2007. Similarly, the fitting groove 2013 of the quartz glass layer 2012 of the quartz base substrate 2003 is formed to a position reaching the quartz base substrate 2003 so that the quartz base substrate 2003 is exposed to the bottom of the fitting groove 2013.

This can reduce the influence of an error in the height direction of the optical waveguide layer 2008 of the quartz-based PLCs 2001 and 2002 on the quartz-based substrate 2003 when fitting the spacer fibers 2006 in the fitting grooves 2007 and 2013. That is, when the optical waveguide layer 2008 is formed on the Si substrate 2009, an error occurs in the thickness of the optical waveguide layer 2008. However, since a polished very flat substrate is used as the Si substrate 2009, the core position from the Si substrate 2009 is accurately determined.

In this way, as shown in fig. 1D, the spacer optical fiber 2006 fitted in the fitting groove 2007 is in contact with the Si substrate 2009 exposed at the bottom of the fitting groove 2007. Further, the spacer fiber 2006 fitted in the fitting groove 2013 is in contact with the quartz-based substrate 2003 exposed to the bottom of the fitting groove 2013. This makes it possible to determine the relative heights of the core positions in the two quartz-based PLCs 2001 and 2002 with very high accuracy. Therefore, high accuracy on the order of submicron can be expected.

Further, the fitting grooves 2007 and 2013 are formed by photolithography. Therefore, the width (the dimension in the left-right direction of fig. 1D), the length (the dimension in the left-right direction of fig. 1B and 1C), and the position of the fitting grooves 2007 and 2013 can be determined with very high accuracy. Accordingly, the axis deviation of the optical waveguide layer 2008 in the direction in the plane of the waveguide layer can be aligned with very high accuracy.

Further, the spacer fibers 2006 having the same diameter are fitted in the four fitting grooves 2013 on the quartz-based substrate 2003 side, the fitting grooves 2007 on the quartz-based PLC2001 side are fitted on two of the four spacer fibers 2006, and the fitting grooves 2007 on the quartz-based PLC2002 side are fitted on the remaining two spacer fibers 2006. Thus, the tilt of the quartz-based PLCs 2001 and 2002 with respect to the quartz-based substrate 2003 can be made small enough to be negligible.

When the above-described structure is adopted, the core positions of the two quartz-based PLCs 2001 and 2002 with respect to the quartz-based substrate 2003 are determined with high accuracy an array of cores 2011 is formed on every of the opposing connection end faces 11 and 12 of the two quartz-based PLCs 2001 and 2002, when the quartz-based PLCs 2001 and 2002 are mounted on the quartz-based substrate 2003, the positions of the cores 2011 of the two quartz-based PLCs 2001 and 2002 are aligned on the same line, and low-loss connection of light can be achieved.

Note that in this embodiment, an example has been described in which the quartz glass layer 2012 of the quartz-based substrate 2003 is manufactured by the same process as that of the optical waveguide layer 2008 of the quartz-based PLCs 2001 and 2002.

Further, fig. 1A to 1D show such an example as follows: the quartz substrate has fitting grooves 2007 and 2013 formed therein such that the direction orthogonal to the connection end faces 11 and 12 of the PLCs 2001 and 2002 is the longitudinal direction of the fitting grooves 2007 and 2013.

In the arrangement of the fitting grooves 2007 and 2013 as shown in fig. 1A to 1D, if the length of the spacer fiber 2006 is equal to the length of the fitting grooves 2007 and 2013, the positions of the quartz-based PLCs 2001 and 2002 in the z-axis direction (the optical axis direction and the left-right direction of fig. 1A to 1C) are determined only.

Here, if the length of the spacer fiber 2006 is set to be smaller than the length of the fitting grooves 2007 and 2013, the positions of the quartz-based PLCs 2001 and 2002 in the z-axis direction cannot be determined only from a different perspective, the position in the z-axis direction cannot be determined only means that the quartz-based PLCs 2001 and 2002 can be slidably adjusted in the z-axis direction as if they were the components mounted on the rails even after mounting.

Therefore, even if there is a small error in the lengths of the quartz-based PLCs 2001 and 2002 in the optical axis direction, the quartz-based PLCs 2001 and 2002 can be slid and adjusted in the z-axis direction so that the gap between the quartz-based PLCs 2001 and 2002 becomes as small as possible. The smaller the gap between the quartz-based PLCs 2001 and 2002, the smaller the optical loss. Therefore, a lower loss connection can be achieved by having the quartz-based PLCs 2001 and 2002 have a slidably adjustable structure. Further, since the accuracy in the optical axis direction can be low when mounting the quartz-based PLCs 2001 and 2002, the mounting operation can be simplified.

In the example shown in fig. 1A to 1D, the longitudinal directions of the fitting grooves 2007 and 2013 are set to be parallel to the optical axis direction of the light exiting from the quartz-based PLC2002 to the quartz-based PLC2001 and the optical axis direction of the light entering the quartz-based PLC 2001.

On the other hand , as shown in fig. 2A to 2C, when the longitudinal direction of the fitting grooves 2007 and 2013 is slightly inclined from the optical axis direction, the positions of the quartz-based PLCs 2001 and 2002 in the z-axis direction can be determined only, fig. 2A is a perspective view of the connection structure of the quartz-based PLCs 2001 and 2002, fig. 2B is an exploded view of parts of the connection structure, fig. 2C is a diagram showing the joint faces of the quartz-based PLCs 2001 and 2002 and the quartz-based substrate 2003, and fig. 2D is a sectional view of the connection structure taken along the xy plane, similar to fig. 1A to 1D.

In the example shown in FIGS. 2A to 2D, if a setting is made such that the gap between the quartz-based PLCs 2001 and 2002 becomes zero when every of the two quartz-based PLCs 2001 and 2002 have designed outer dimensions, there is a concern that the quartz-based PLCs 2001 and 2002 are mechanically interfered with in the vicinity of the connection end faces 11 and 12 of the quartz-based PLCs 2001 and 2002 due to a slight outer diameter error of the quartz-based PLCs 2001 and 2002.

In both cases shown in fig. 1A to 1D and fig. 2A to 2D, the gap between the connection end faces 11 and 12 of the two quartz-based PLCs 2001 and 2002 is filled with an index-matching resin. When the gap is filled with the index matching resin, fresnel reflection of light caused by air existing in the gap between the quartz-based PLCs 2001 and 2002 can be suppressed.

Further, in this embodiment, the quartz-based PLCs 2001 and 2002 are only placed on the quartz-based substrate 2003 in such a manner that they are supported by the spacer fiber 2006, but are not fixed. In this way, the quartz-based PLCs 2001 and 2002 are detachable from the quartz-based substrate 2003, and a pluggable connection can be achieved, in which the necessary quartz-based PLCs 2001 and 2002 can be connected only when necessary, like a connector. This form is known as PPCP (pluggable photonic circuit platform).

In some cases, the quartz-based PLCs 2001 and 2002 may be bonded by filling gaps between the quartz-based substrate 2003 and the quartz-based PLCs 2001 and 2002 with an optical adhesive having a matched index of refraction, or both the quartz-based PLCs 2001 and 2002 may be bonded and fixed after being mounted on the quartz-based substrate 2003. alternatively, of the two quartz-based PLCs 2001 and 2002 may be fixed to the quartz-based substrate 2003, while the other may be detachable.

When the quartz-based PLCs 2001 and 2002 are actually mounted in the form shown in fig. 2A to 2D, it has been confirmed that, at a wavelength of 1.55 μm, connection loss of 0.4dB or less can be achieved in four cores using the quartz-based PLCs 2001 and 2002 having a mode diameter of about 6 μm. The value of this loss indicates that the two quartz-based PLCs 2001 and 2002 can be installed with a position accuracy of a submicron order or less. Since the accuracy of the installation form of this embodiment is high, and also since the structure of this embodiment can make the gap between the quartz-based PLCs 2001 and 2002 as small as possible, such a low loss can be achieved, and therefore, the influence of a positional error such as an axis deviation can be minimized.

Here, it is known that as the beam diameter becomes smaller, the optical loss caused by the axis deviation has a larger influence. More preferably, spot size conversion for increasing the beam diameter is used near the connection end faces of the quartz-based PLCs 2001 and 2002. As a method of spot size conversion, it is preferable to appropriately set a known spot size conversion structure such as a tapered shape that increases the core diameter toward the end face, an inverted tapered shape that decreases the core diameter toward the end face, a segmented structure, a structure in which a second core is added to the inverted tapered shape, or a structure in which a second core layer of a different material is buried.

[ second embodiment ]

Next, a second embodiment of the present invention will be described. Fig. 3A to 3D are schematic views showing a connection structure of an optical waveguide chip according to a second embodiment of the present invention, and in fig. 3A to 3D, the same reference numerals as in fig. 1A to 1D and fig. 2A to 2D denote the same components. Fig. 3A is a perspective view of a connection structure of the quartz-based PLCs 2001a and 2002a, fig. 3B is an exploded view of parts of the connection structure, fig. 3C is a diagram showing bonding surfaces of the quartz-based PLCs 2001a and 2002a and the quartz-based substrate 2003A, and fig. 3D is a sectional view of the connection structure taken along the xy plane.

The basic structure of this embodiment is the same as the th embodiment, in this embodiment, the quartz-based PLCs 2001a and 2002a share a fitting groove formed on the quartz glass layer 2012 of the quartz-based substrate 2003a, that is, two fitting grooves 2013a are formed in the quartz glass layer 2012 in addition, the quartz-based PLCs 2001a and 2002a also share a spacing optical fiber 2006a (spacing member) fitted in the fitting groove 2013a, and only two spacing optical fibers 2006a are used.

As in the th embodiment, two fitting grooves 2007a are formed in every optical waveguide layers 2008 (cladding layers 2010) of the quartz-based PLCs 2001a and 2002a however, since the spacer fibers 2006a are shared by the quartz-based PLCs 2001a and 2002a, the fitting grooves 2007a formed in the optical waveguide layers 2008 of the quartz-based PLC2001a need to reach the connection end face 11 of the quartz-based PLC2001 a.

When the connection structure according to this embodiment is manufactured, the spacer fibers 2006a are fitted in two fitting grooves 2013a formed in the silica glass layer 2012 of the silica-based substrate 2003a, respectively. Then, the two spacer fibers 2006a fitted in the fitting grooves 2013a are fitted in the two fitting grooves 2007a formed in the optical waveguide layer 2008 of the quartz-based PLC2001a such that the bonding surface of the quartz glass layer 2012 and the bonding surface of the optical waveguide layer 2008 (cladding layer 2010) of the quartz-based PLC2001a face each other, as shown in fig. 3B, thereby mounting the quartz-based PLC2001a on the quartz-based substrate 2003 a.

Similarly, the two spacer fibers 2006a fitted in the fitting grooves 2013a are fitted in the two fitting grooves 2007a formed in the optical waveguide layer 2008 of the quartz-based PLC2002a such that the bonding surface of the quartz glass layer 2012 and the bonding surface of the optical waveguide layer 2008 (cladding layer 2010) of the quartz-based PLC2002a face each other, thereby mounting the quartz-based PLC2002a on the quartz-based substrate 2003 a.

As described above, in this embodiment, compared with the th embodiment in which the quartz-based PLCs 2001 and 2002 use different spacer fibers 2006 and different fitting grooves 2007 and 2013, since the influence of the formation error of the spacer fiber 2006a, the formation error of the fitting grooves 2007a and 2013a, and the like is hard to exert, more accurate mounting can be expected.

Further, when the quartz-based PLCs 2001a and 2002a share the fitting grooves 2013a on the quartz-based substrate 2003a side, the accuracy specification of the fitting grooves 2013a can be greatly relaxed, that is, when the four fitting grooves 2013 on the quartz-based substrate 2003 side are formed to correspond to the fitting grooves 2007 of the quartz-based PLCs 2001 and 2002 as in the embodiment, it is necessary to ensure the accuracy of the depth and width of the fitting grooves 2013 to be submicron accuracy so that the relative positions of the two quartz-based PLCs 2001 and 2002 are not shifted.

In addition , in this embodiment, the quartz-based PLCs 2001a and 2002a share the fitting groove 2013a on the quartz-based base 2003a side, and therefore, if the two fitting grooves 2013a are formed to have the same absolute accuracy in the longitudinal direction of the fitting groove 2013a, the relative positional accuracies of the two quartz-based PLCs 2001a and 2002a do not change.

Thus, it is not always necessary for the fitting groove 2013a on the quartz-based base 2003a side to perform etching or the like using a material formed of two layers such as a substrate and a glass layer as described in the embodiment, for example, even if the fitting groove 2013a is formed by etching or processing (such as cutting) in a substrate made of quartz glass, the positional accuracy between the quartz-based PLCs 2001a and 2002a is not affected.

[ third embodiment ]

Next, a third embodiment of the present invention will be described. Fig. 4A and 4B are schematic views showing a connection structure of an optical waveguide chip according to a third embodiment of the present invention, and in fig. 4A and 4B, the same reference numerals as in fig. 1A to 1D, fig. 2A to 2D, and fig. 3A to 3D denote the same components.

In this embodiment, fitting grooves 2014 are added per PLC in the optical waveguide layer 2008 (cladding layer 2010) of every of the two quartz-based PLCs 2001b and 2002b in the connection structure described in the embodiment, the longitudinal directions of the fitting grooves 2014 in the connection face being perpendicular to the optical axis direction of the light exiting from the quartz-based PLC 39 b to the quartz-based PLC2001b and the optical axis direction of the light entering the quartz-based PLC2001b (the left-right direction of FIG. 4A) in the connection face.

In the quartz glass layer 2012 of the quartz-based substrate 2003b, fitting grooves 2015 are added at positions facing the fitting grooves 2014 when the quartz-based PLCs 2001b and 2002b are mounted on the quartz-based substrate 2003b as described above, since fitting grooves 2014 are formed in PLCs, a total of two fitting grooves 2015 are formed in the quartz glass layer 2012, that is, fitting grooves 2015 formed at positions facing the fitting grooves 2014 of the quartz-based PLC2001b and fitting grooves 2015 formed at positions facing the fitting grooves 2014 of the quartz-based PLC2002 b.

When the connection structures of the quartz-based PLCs 2001b and 2002b are manufactured, spacer fibers 2006 are respectively fitted in fitting grooves 2013 on the quartz-based substrate 2003b side, and at the same time, similar spacer fibers 2016 are respectively fitted in fitting grooves 2015. Then, the spacer fibers 2006 and 2016 fitted in the fitting grooves 2013 and 2015 are fitted in the fitting grooves 2007 and 2014 on the quartz-based PLC2001b side so that the bonding surface of the quartz-based substrate 2003b and the bonding surface of the quartz-based PLC2001b face each other, thereby mounting the quartz-based PLC2001b on the quartz-based substrate 2003 b. Similarly, the spacer fibers 2006 and 2016 fitted in the fitting grooves 2013 and 2015 are fitted in the fitting grooves 2007 and 2014 on the quartz-based PLC2002b side so that the bonding surface of the quartz-based substrate 2003b and the bonding surface of the quartz-based PLC2002b face each other, thereby mounting the quartz-based PLC2002b on the quartz-based substrate 2003 b.

Fig. 4B shows the bonding surfaces of the quartz-based PLCs 2001c and 2002c and the quartz-based substrate 2003c, which has the same structure as the second embodiment. Also in the example shown in fig. 4B, fitting grooves 2014 and 2015 are formed in the quartz-based PLCs 2001c and 2002c and the quartz-based substrate 2003 c.

When the connection structures of the quartz-based PLCs 2001c and 2002c are manufactured, spacer fibers 2006a are fitted in the fitting grooves 2013a on the quartz-based substrate 2003c side, respectively, and at the same time, spacer fibers 2016 are fitted in the fitting grooves 2015, respectively. Then, the spacer fibers 2006a and 2016 fitted in the fitting grooves 2013a and 2015 are fitted in the fitting grooves 2007a and 2014 on the quartz-based PLC2001c side so that the bonding surface of the quartz-based substrate 2003c and the bonding surface of the quartz-based PLC2001c face each other, thereby mounting the quartz-based PLC2001c on the quartz-based substrate 2003 c. Similarly, the spacer fibers 2006a and 2016 fitted in the fitting grooves 2013a and 2015 are fitted in the fitting grooves 2007a and 2014 on the quartz-based PLC2002 c side so that the bonding surface of the quartz-based substrate 2003c and the bonding surface of the quartz-based PLC2002 c face each other, thereby mounting the quartz-based PLC2002 c on the quartz-based substrate 2003 c.

Since the fitting groove 2014 formed in the quartz-based PLCs 2001b, 2002b, 2001c, and 2002c is orthogonal to the optical axis direction, the layout of the optical waveguides and the position of the fitting groove 2014 are appropriately set to prevent the fitting groove 2014 from dividing the optical waveguides. Like the fitting grooves 2007 and 2007a, the fitting groove 2014 is formed to such a depth that the Si substrate is exposed to the bottom of the fitting groove 2014, and the spacer optical fiber 2016 fitted in the fitting groove 2014 is in contact with the Si substrate.

Further, like the fitting grooves 2013 and 2013a, when a fitting groove 2015 is formed in the quartz glass layer on the quartz base substrate 2003b or 2003c, the fitting groove 2015 is formed to such a depth that the quartz base substrate 2003b or 2003c is exposed to the bottom of the fitting groove 2015, and the spacer fiber 2016 fitted in the fitting groove 2015 is in contact with the quartz base substrate 2003b or 2003 c.

With the above-described structure, in this embodiment, the positions of the quartz-based PLCs 2001b, 2002b, 2001c, and 2002c in the z-axis direction can be determined exclusively .

However, in this embodiment, in consideration of the influence of the outside dimension errors of the quartz-based PLCs 2001b, 2002b, 2001c, and 2002c, the widths of the fitting grooves 2014 and 2015 in the optical axis direction are set to be slightly wider than the width (diameter) of the spacer fiber 2016 fitted in the fitting grooves 2014 and 2015. Further, the lengths of the fitting grooves 2007, 2013, 2007a, and 2013a in the optical axis direction are set to be slightly longer than the lengths of the spacer fibers 2006 and 2006a fitted in the fitting grooves 2007, 2013, 2007a, and 2013 a.

By the setting of the width and the length, even if the outside dimensions of the quartz-based PLCs 2001b, 2002b, 2001c, and 2002c are erroneous, the quartz-based PLCs 2001b, 2002b, 2001c, and 2002c can be slid in the z-axis direction by using the gap between the spacer fibers 2016 fitted in the fitting grooves 2014 and 2015 and the gap between the spacer fibers 2006 and 2006a fitted in the fitting grooves 2007, 2013, 2007a, and 2013a and the fitting grooves 2007, 2013, 2007a, and 2013a to adjust their positions.

Therefore, in this embodiment, the following problems can be avoided: the two quartz-based PLCs 2001b and 2002b (or 2001c and 2002c) as described above are mechanically interfered, and the two quartz-based PLCs 2001b and 2002b (or 2001c and 2002c) cannot be installed.

Further, in this embodiment, after installation, the quartz-based PLCs 2001b and 2002b (or 2001c and 2002c) can be slid and adjusted in the z-axis direction so that the gap between the quartz-based PLCs 2001b and 2002b (or 2001c and 2002c) becomes as small as possible, as in the embodiment.

[ fourth embodiment ]

Next, a fourth embodiment of the present invention will be described. Fig. 5A and 5B are schematic views showing a connection structure of an optical waveguide chip according to a fourth embodiment of the present invention, and in fig. 5A and 5B, the same reference numerals as in fig. 1A to 1D, fig. 2A to 2D, fig. 3A to 3D, fig. 4A and 4B denote the same components.

FIG. 5A is a plan view showing a connection structure in which three quartz-based PLCs 2017, 2018, and 2019 are mounted on a quartz-based substrate 2003b when viewed from an upper side, the structures of the PLCs 2017 and 2019 are the same as those of the quartz-based PLCs 2001b and 2002b explained with reference to FIG. 4A, and in another aspect , the structure of the PLC 2018 is the same as those of the quartz-based PLCs 2001 and 2002 explained with reference to FIGS. 1A to 1D.

FIG. 5B is a plan view showing a connection structure in which three quartz-based PLCs 2017a, 2018a, and 2019a are mounted on a quartz-based substrate 2003c when viewed from an upper side.the structures of the PLCs 2017a and 2019a are the same as those of the quartz-based PLCs 2001c and 2002c explained with reference to FIG. 4B. in another aspect , the structure of the PLC 2018a is the same as those of the quartz-based PLCs 2001a and 2002a explained with reference to FIGS. 3A to 3D. however, since the spacer fiber 2006a is shared by the three quartz-based PLCs 2017a, 2018a, and 2019a, the fitting groove 2007a formed in the optical waveguide layer of the quartz-based PLC 2018a located at the center needs to reach the left and right end surfaces of the quartz-based PLC 2018 a.

In this embodiment, the three quartz-based PLCs 2017, 2018, 2019(2017a, 2018a, 2019a) are arranged on the same line and mounted by the same passive alignment method as described above.two quartz-based PLCs 2017, 2019(2017a, 2019a) on both sides are mounted on a quartz-based substrate 2003b (2003c) and then adhesively secured and integrated with the quartz-based substrate 2003b (2003 c). in another aspect of , the centrally located quartz-based PLC 2018(2018a) has a pluggable detachable structure.the quartz-based PLC 2018(2018a) can be used as a simple evaluation kit for inspection or sensing.

As can be seen from this embodiment, the present invention can be applied without depending on the number of optical waveguide chips (PLCs) connected. For example, instead of connecting three optical waveguide chips as in this embodiment, four or more optical waveguide chips may also be connected.

Further, in the above-described embodiments, an example has been described in which all the inputs/outputs are connected at the opposite connection end faces (all the connection end faces are parallel), however, the present invention is not limited thereto.

Note that in the th to fourth embodiments, a quartz-based Planar Lightwave Circuit (PLC) of a thin glass film formed on a silicon substrate has been described as an optical waveguide chip by way of example, however, the present invention can be applied to any optical waveguide chip including a waveguide mechanism, for example, as a material of a substrate or an optical waveguide, quartz, a polymer made of an organic substance, a semiconductor or compound semiconductor waveguide using Si, silicon nitride (SiN), gallium arsenide, indium phosphide (InP), or the like, and a dielectric such as Lithium Niobate (LN), Periodically Polarized Lithium Niobate (PPLN), or Lithium Tantalate (LT) can be used in addition to quartz glass.

In the th to fourth embodiments, each PLC has two or more fitting grooves 2007 or 2007 a. the fitting grooves 2013 or 2013a formed in the quartz-based substrate 2003, 2003a to 2003c need only be set in number according to the fitting grooves 2007 or 2007 a. as described above, the number of the fitting grooves 2013 or 2013a is equal to the total number of the fitting grooves 2007 or 2007a (fig. 1, 2, and 4A), or is smaller than the total number of the fitting grooves 2007 or 2007a (fig. 3). the spacing optical fiber 2006 or 2006a needs only be set in number according to the fitting groove 2007, 2007a, 2013, or 2013a, the number of the spacing optical fiber 2006 or 2006a is equal to the total number of the fitting grooves 2007 or 2007a (fig. 1, 2, and 4A), or is smaller than the total number of the fitting grooves 2007 or 2007a (fig. 3).

Further, in the third and fourth embodiments, each PLC has or more fitting grooves 2014 the fitting grooves 2015 formed in the quartz-based substrate 2003b or 2003c only need to be provided as many as the fitting grooves 2014 the spacer fibers 2016 are provided in number according to the fitting grooves 2014 and 2015.

In the to fourth embodiments, there have been described examples in which the fitting grooves 2007, 2007a, 2013a, 2014, and 2015 formed in the quartz-based PLCs 2001, 2001a to 2001c, 2002a to 2002c, 2017 to 2019, and 2017a to 2019a and the quartz-based substrates 2003 and 2003a to 2003c are grooves each having a rectangular cross section, however, grooves whose groove widths are narrowed toward the substrates 2009, 2003, and 2003a to 2003c may be used, for example, grooves each having a V-shaped or W-shaped cross section or grooves each having a U-shaped cross section, furthermore, in the to fourth embodiments, the shape of each of the fitting grooves 2007, 2007a, 2013a, 2014, and 2015 as viewed from the upper side is 2015 rectangular.

In addition, in the th through fourth embodiments, the fitting grooves 2007, 2007a, and 2014 have the same depth, and the fitting grooves 2013, 2013a, and 2015 have the same depth.

In addition, in the th to fourth embodiments, cylindrical spacer fibers 2006, 2006a, and 2016 are used as spacer members, however, the present invention is not limited thereto the material of the spacer members may be any material, for example, inorganic substances such as glass, metal, or polymer, furthermore, the shape is not limited as long as it can be suitably fitted in of the fitting grooves 2007, 2007a, 2013a, 2014, and 2015.

[ fifth embodiment ]

Next, a fifth embodiment of the present invention will be described. Fig. 6A and 6B are schematic views showing a connection structure of an optical waveguide chip according to a fifth embodiment of the present invention, and in fig. 6A and 6B, the same reference numerals as in fig. 1A to 1D, fig. 2A to 2D, and fig. 3A to 3D denote the same components. Fig. 6A is a sectional view of the connection structure, and fig. 6B is a diagram showing a bonding surface of the optical waveguide chip.

Fig. 6A is a sectional view showing the following connection structure: in which an optical waveguide chip (laser chip) 2020 and an optical waveguide chip 2021 that transmits light from the optical waveguide chip 2020 to an optical fiber 2022 are mounted on a substrate 2026. As the optical waveguide chip 2020, a DFB (distributed feedback) laser chip made of a III-V group material such as InP is used. In addition to the DFB laser, a DBR (distributed bragg reflector) laser, an SOA (semiconductor optical amplifier), or the like can be used. Electrical wires and connection pads electrically connected to a driver configured to drive the DFB laser are not shown in the figure.

Here, the optical waveguide chip 2020 includes the above-described DFB laser 2023 and optical waveguide layer 2024. the structure in which two fitting grooves 2007 are formed in the cladding layer of the optical waveguide layer 2024 is the same as that described in the embodiment. a spot-size converter 2025 that makes the diameter of the light beam from the DFB laser 2023 close to the diameter of the core section in the optical waveguide layer 2008 of the optical waveguide chip 2021 is integrated in the vicinity of the connection end face of the optical waveguide layer 2024 with the optical waveguide chip 2021.

The optical waveguide chip 2020 is mounted such that output light is connected to the core of the connection end face of the optical waveguide chip 2021 by the PPCP technique of the present invention. The structure in which the fitting grooves 2007 and 2014 are formed in the cladding layer of the optical waveguide layer 2008 of the optical waveguide chip 2021 is the same as that described in the third embodiment. The light that has propagated through the optical waveguide layer 2008 of the optical waveguide chip 2021 is output from the end face on the opposite side of the optical waveguide chip 2020 to the optical fiber 2022 via a lens (not shown), or directly to the optical fiber 2022.

The substrate 2026 according to this embodiment is made of Si, ceramics such as LTCC (low temperature co-fired ceramic), aluminum nitride, or the like in of the manufacturing process and the post-process (etching or machining) of the substrate 2026, fitting grooves 2013a and 2015 to be fitted on the spacing fibers 2006 are formed.

When manufacturing the connection structure of the optical waveguide chips 2020 and 2021, two spacer fibers 2006 are fitted in fitting grooves 2013a on the substrate 2026 side, and at the same time, a spacer fiber 2016 described in the third embodiment is fitted in the fitting groove 2015, then, the spacer fibers 2006 and 2016 fitted in the fitting grooves 2013a and 2015 are fitted in the fitting grooves 2007 and 2014 on the optical waveguide chip 2020 side so that the bonding face of the substrate 2026 and the bonding face of the optical waveguide chip 2020 face each other, thereby mounting the optical waveguide chip 2020 on the substrate 2026.

Conventionally, in order to mount a laser chip by active alignment, a complicated mounting process is required in which light is output from the laser chip, light is input to an optical waveguide chip of a connection partner, and the output light of the optical waveguide chip is monitored in step .

As described in embodiment , this embodiment can be applied to any optical waveguide chip other than a light emitting element such as a laser chip, for example, an optical function element (switch or wavelength multiplexer/demultiplexer), an optical modulation element, a light emitting element, a light receiving element, a wavelength conversion element, or a light amplifying element having a light propagating/guiding mechanism.

[ principles of sixth to ninth embodiments ]

Fig. 7A to 7D are schematic diagrams showing connection structures of optical waveguide chips which are the basis of sixth to ninth embodiments of the present invention. Fig. 7A is a perspective view of a connection structure of an optical waveguide chip, fig. 7B is an exploded view of parts of the connection structure, fig. 7C is a diagram showing a bonding surface of the optical waveguide chip with a substrate, and fig. 7D is a sectional view of the connection structure taken along an xy plane.

In fig. 7A to 7D, a total of seven members, that is, the quartz-based PLCs 3001 and 3002, which are two optical waveguide chips each formed of a quartz glass layer including a Si substrate and a waveguide layer, the quartz-based substrate 3003, which is manufactured by the same method as the quartz-based PLCs 3001 and 3002 and does not include a waveguide, and the four spacer fibers 3006 are combined, thereby forming a connection structure.

The connection structures shown in fig. 7A-7D are configured to be able to propagate an input optical signal 3005 and output it as an output optical signal 3004 via the quartz-based PLCs 3001 and 3002.

As shown in fig. 7D, the quartz-based PLC3001 has a structure in which an optical waveguide layer 3008 is formed on a Si substrate 3009, the optical waveguide layer 3008 is formed of a cladding layer 3010 and a core 3011, the cladding layer 3010 is made of quartz glass, and a core 2011 is formed in a cladding layer 2010 and is made of quartz glass containing dopants, further, fitting grooves 3007 each having a rectangular shape in a plan view are formed in the cladding layer 3010, the structure of the quartz-based PLC3002 is the same as that of the quartz-based PLC3001, fig. 7C shows a junction surface of the optical waveguide layer 3008 (cladding layer 3010) and the quartz-based base 3003 of the quartz-based PLCs 3001 and 3002, and it is apparent from fig. 7C that two fitting grooves 3007 are formed in PLCs.

As shown in fig. 7A and 7B, the quartz-based PLC3001 and the quartz-based PLC3002 are arranged side by side such that the connection end surfaces 11 and 12 face each other. Two quartz-based PLCs 3001 and 3002 are mounted on the quartz-based substrate 3003.

A quartz glass layer 3012 made of the same material as the cladding layer 3010 of the quartz-based PLCs 3001 and 3002 is formed on the surface of the quartz-based substrate 3003 on which the quartz-based PLCs 3001 and 3002 are mounted. In the quartz glass layer 3012, a fitting groove 3013 having the same shape as the fitting groove 3007 is formed at a position facing the fitting groove 3007 of the quartz-based PLCs 3001 and 3002 when the quartz-based PLCs 3001 and 3002 are mounted on the quartz-based substrate 3003, as will be described later.

FIG. 7C shows the interface of the quartz glass layer 3012 with the quartz-based PLCs 3001 and 3002 As described above, since two assembly slots 3007 are formed in PLCs, a total of four assembly slots 3013 are formed in the quartz glass layer 3012, namely, two assembly slots 3013 formed at positions facing the assembly slots 3007 of the quartz-based PLC3001 and two assembly slots 3013 formed at positions facing the assembly slots 3007 of the quartz-based PLC 3002.

To fabricate the connection structure shown in fig. 7A, spacer fibers 3006 are respectively fitted into four fitting grooves 3013 formed in a silica glass layer 3012 of a silica-based substrate 3003. Then, the two spacer fibers 3006 fitted in the fitting grooves 3013 of the silica glass layer 3012 are fitted in the two fitting grooves 3007 formed in the optical waveguide layer 3008 of the silica-based PLC3001 so that the junction surface of the silica glass layer 3012 and the junction surface of the optical waveguide layer 3008 (cladding layer 3010) of the silica-based PLC3001 face each other as shown in fig. 7B, that is, so that the Si substrate 3009 is located on the upper side and the optical waveguide layer 3008 is located on the lower side, thereby mounting the silica-based PLC3001 on the silica-based substrate 3003.

Similarly, two spacer fibers 3006 fitted in the fitting grooves 3013 of the quartz glass layer 3012 are fitted in two fitting grooves 3007 formed in the optical waveguide layer 3008 of the quartz-based PLC3002 so that the junction surface of the quartz glass layer 3012 and the junction surface of the optical waveguide layer 3008 (cladding layer 3010) of the quartz-based PLC3002 face each other, thereby mounting the quartz-based PLC3002 on the quartz-based substrate 3003.

In this way, the quartz-based PLCs 3001 and 3002 may be mounted on the quartz-based substrate 3003 such that the connection end surfaces 11 and 12 of the quartz-based PLCs 3001 and 3002 closely face each other, and optical connection between the quartz-based PLCs 3001 and 3002 may be achieved.

As shown in FIG. 7A, an input optical signal 3005 that has entered the quartz-based PLC3002 propagates through the optical waveguide layer 3008 of the quartz-based PLC3002, exits the quartz-based PLC3002, enters the quartz-based PLC3001, propagates through the optical waveguide layer 3008 of the quartz-based PLC3001, and exits the quartz-based PLC3001 as an output optical signal 3004.

As is apparent from fig. 7D, the fitting groove 3007 of the optical waveguide layer 3008 of the quartz-based PLCs 3001 and 3002 is formed to a position reaching the Si substrate 3009 so that the Si substrate 3009 is exposed to the bottom of the fitting groove 3007. Similarly, the fitting groove 3013 of the quartz glass layer 3012 of the quartz-based substrate 3003 is formed to a position reaching the quartz-based substrate 3003 so that the quartz-based substrate 3003 is exposed to the bottom of the fitting groove 3013.

This can reduce the influence of errors in the height direction of the optical waveguide layer 3008 of the quartz-based PLCs 3001 and 3002 on the quartz-based substrate 3003 when the spacer fibers 3006 are fitted in the fitting grooves 3007 and 3013. That is, when the optical waveguide layer 3008 is formed on the Si substrate 3009, an error occurs in the thickness of the optical waveguide layer 3008. However, since a polished very flat substrate is used as the Si substrate 3009, the core position from the Si substrate 3009 is accurately determined.

Thus, as shown in FIG. 7D, spacer fiber 3006 mounted in mounting slot 3007 is in contact with Si substrate 3009 exposed at the bottom of mounting slot 3007. In addition, the spacer fibers 3006 mounted in the mounting slots 3013 are in contact with the quartz-based substrate 3003 exposed to the bottom of the mounting slots 3013. This makes it possible to determine the relative heights of the core positions in the two quartz-based PLCs 3001 and 3002 with very high accuracy. Therefore, high accuracy on the order of submicron can be expected.

Further, the fitting grooves 3007 and 3013 are formed by photolithography. Therefore, the width (dimension in the left-right direction of fig. 7D), the length (dimension in the left-right direction of fig. 7B and 7C), and the position of the fitting grooves 3007 and 3013 can be determined with very high accuracy. Accordingly, the axial deviation of the optical waveguide layer 3008 in the direction in the plane of the waveguide layer can be aligned with very high accuracy.

Further, spacer fibers 3006 having the same diameter are fitted in the four fitting grooves 3013 on the quartz-based substrate 3003 side, fitting grooves 3007 on the quartz-based PLC3001 side are fitted on two of the four spacer fibers 3006, and fitting grooves 3007 on the quartz-based PLC3002 side are fitted on the remaining two spacer fibers 3006. Thus, the tilt of the quartz-based PLCs 3001 and 3002 with respect to the quartz-based substrate 3003 can be made small enough to be negligible.

When the above-described structure is adopted, the core positions relative to the quartz-based substrate 3003 in the two quartz-based PLCs 3001 and 3002 are determined with high accuracy, an array of cores 3011 is formed on every of the opposing connection end faces 11 and 12 of the two quartz-based PLCs 3001 and 3002 when the quartz-based PLCs 3001 and 3002 are mounted on the quartz-based substrate 3003, the positions of the cores 3011 in the two quartz-based PLCs 3001 and 3002 are aligned on the same line, and low-loss connection of light can be achieved.

However, in the connection structure shown in FIGS. 7A to 7D, since the optical waveguide chip is aligned in accordance with the accuracy of the components such as the size of the optical waveguide chip itself, the position of the groove, the shape of the groove, and the shape of the spacer, it is a necessary condition that the accuracy of the components is high.

When the gap between the adjacent optical waveguide chips (between the quartz-based PLCs 3001 and 3002) is filled with the index matching resin or the like, the influence of the roughening of the connection end surfaces of the optical waveguide chips can be reduced. However, if the gaps between the optical waveguide chips are filled with an adhesive such as an index-matching resin to fix them, the reliability of the adhesive may be lowered due to the roughening of the connection end faces of the optical waveguide chips. Further, if chipping (cracking) occurs in the connection end face of the optical waveguide chip by dicing or the like, the optical loss of the connection end face may be reduced.

In conventional active alignment mounting, the connection end surface of each optical waveguide chip is polished or etched after dicing to remove the roughening of the connection end surface, thereby ensuring reliability. However, when the connection end surface is polished, a polishing error is generated, and an angular deviation of the connection end surface occurs. Therefore, as shown in the perspective view of fig. 8A and the plan view of fig. 8B, when additional processing of the connection end faces 11 and 12 of the optical waveguide chips (the quartz-based PLCs 3001 and 3002) is applied to the connection structure shown in fig. 7A to 7D, errors are generated in the angles of the connection end faces 11 and 12 and the relative angles of the fitting grooves 3007 and 3013.

According to the angle error, when the optical waveguide chip is mounted on the quartz-based substrate 3003, the gap between the two optical waveguide chips is changed, and in the optical waveguide array formed in the optical waveguide layer 3008 of each optical waveguide chip, the chip connection loss of the core 3011 located in the portion where the gap is wider increases, and as a result, the loss difference in the optical waveguide array may increase.

Therefore, in the present invention, based on the connection structure described with reference to fig. 7A to 7D, the influence of the angular error deviation caused by the additional processing of the connection end surface is reduced.

[ sixth embodiment ]

An optical connection structure according to a sixth embodiment of the present invention will be described below. Fig. 9A and 9B are schematic views showing a connection structure of an optical waveguide chip according to a sixth embodiment of the present invention, and in fig. 9A and 9B, the same reference numerals as in fig. 7A to 7D, 8A, and 8B denote the same components. Fig. 9A is a perspective view of the connection structure of the optical waveguide chip, and fig. 9B is a plan view of the connection structure as viewed from the upper side.

Note that various functional circuits configured to process signals, such as switches and wavelength multiplexers/demultiplexers, are mounted on the optical waveguide chip as necessary. However, this embodiment does not depend on the circuit arrangement in the optical waveguide chip and the function of the circuit. In practice, appropriate optical circuits are formed in the optical waveguide chip in an arrangement that avoids the fitting grooves. However, since this embodiment does not depend on the arrangement of the circuit, fig. 9A and 9B show an example including only a linear waveguide, and other circuit arrangements are omitted for the sake of simple description.

Like the above-described quartz-based PLCs 3001 and 3002, each of the quartz-based PLCs 3001a and 3002a have a structure in which an optical waveguide layer 3008 is formed on a Si substrate 3009. the structure of the optical waveguide layer 3008 is the same as that described with reference to FIGS. 7A to 7D. fitting grooves 3007 are formed in the cladding layer of the optical waveguide layer 3008. like the quartz-based PLCs 3001 and 3002, two fitting grooves 3007 are formed in each of the quartz-based PLCs 3001a and 3002 a.

The structure of the quartz-based substrate 3003 is the same as described with reference to fig. 7A to 7D. Further, a method of mounting the quartz-based PLCs 3001a and 3002a on the quartz-based substrate 3003 and implementing optical connection between the quartz-based PLCs 3001a and 3002a is the same as the method described with reference to fig. 7A to 7D, and a description thereof will be omitted.

The assembly grooves 3007 on the quartz-based PLCs 3001a and 3002a side are formed to such a depth that the Si substrate 3009 is exposed to the bottom of the assembly grooves 3007, and the spacer fibers 3006 (spacer members) assembled in the assembly grooves 3007 are in contact with the Si substrate 3009. Similarly, the fitting groove 3013 on the quartz-based substrate 3003 side is formed to such a depth that the quartz-based substrate 3003 is exposed to the bottom of the fitting groove 3013, and the spacer optical fiber 3006 fitted in the fitting groove 3013 is in contact with the quartz-based substrate 3003. Therefore, high accuracy on the order of submicron can be expected.

Further, in this embodiment, the longitudinal direction of the fitting grooves 3007 and 3013 is set to be parallel to the z-axis direction (the optical axis direction of the light exiting from the quartz-based PLC3002 a to the quartz-based PLC3001a and the optical axis direction of the light entering the quartz-based PLC3001a or the left-right direction of fig. 9A and 9B). As the spacer member, cylindrical spacer fibers 3006 each having a diameter of 125 μm were used. The length of the spacer fiber 3006 in the z-axis direction is set to be smaller than the length of the fitting grooves 3007 and 3013. Therefore, in this embodiment, the quartz-based PLCs 3001a and 3002a can be slide-adjusted in the z-axis direction even after installation.

Thus, the quartz-based PLCs 3001a and 3002a can be slid and adjusted in the z-axis direction so that the gap between the quartz-based PLCs 3001a and 3002a becomes as small as possible. The smaller the gap between the quartz-based PLCs 3001a and 3002a, the less optical loss. Therefore, it is possible to realize a lower loss connection by having the quartz-based PLCs 3001a and 3002a have a slidably adjustable structure.

In another aspect, after mounting, the gap between the quartz-based PLCs 3001a and 3002a is filled with an adhesive (not shown) to fix them, at this time, the connection end faces 11 and 12 (incident/exit end faces) of the quartz-based PLCs 3001a and 3002a facing each other are accurately polished by performing mechanical polishing in advance, by which the roughening of the connection end faces 11 and 12 becomes small enough to be negligible, and there is no chipping (cracking) caused by cutting.

However, as described above, a slight angle error may be generated in the connection end faces 11 and 12 by polishing. In the example shown in fig. 9B, the inclination of the connection end surface 12 is shown to be large for easy understanding. The actual angular error of the connecting end faces 11 and 12 in the plane of the substrate is of the order of sub-degrees, for example about 0.4 °.

However, even with this degree of angular error, there is a concern that: the interval between the quartz-based PLCs 3001a and 3002a changes between the cores 3011 in the optical waveguide array, and the dependence of the loss on the optical waveguide ports (the entrance/exit end faces of the cores 3011) increases. That is, there is a fear that: as the number of the cores 3011 in the optical waveguide array in the optical waveguide layer 3008 becomes larger, the influence becomes larger as the pitch between the cores 3011 becomes larger, and as the width of the connection end faces 11 and 12 in the x-axis direction (the direction perpendicular to the optical axis direction in the substrate plane) becomes larger.

In this embodiment, pitch conversion sections 3014 and 3015 that make narrower the x-axis direction interval between the cores 3011 of the optical waveguide array on the connection end faces 11 and 12 than the x-axis direction interval between the cores 3011 in the sections away from the connection end faces 11 and 12 are provided in the vicinity of the connection end faces 11 and 12 of the quartz-based PLCs 3001a and 3002 a. In this embodiment, the x-axis direction interval between the cores 3011 of the optical waveguide array on the connection end faces 11 and 12 is set to about 20 μm.

The interval between the optical waveguides (cores 3011) in the optical waveguide array can be arbitrarily narrowed in a range of: the restriction of light propagation in the optical waveguide can be sufficiently ensured and crosstalk caused by light leakage from other optical waveguides has no influence. For example, in the case of, for example, a Si waveguide array using Si for the core, since the light confinement effect is sufficiently large, the interval between the optical waveguides can be made narrower. According to this embodiment, an increase in loss caused by an angular error of the connection end faces 11 and 12 and a variation in loss between optical waveguide ports can be reduced.

In the structures shown in fig. 7A to 7D, if there are eight optical waveguide ports at an optical waveguide interval of about 250 μm, the x-axis direction interval between both ends of the optical waveguide array is 1.75 mm. Here, if the widths of the quartz-based PLCs 3001 and 3002 in the x-axis direction are 8mm, and the actual angle errors of the connection end faces 11 and 12 in the substrate plane (in the sheet surface of fig. 9B) are 0.4 ° with respect to the design values, a difference of about 8 × tan (0.4 °) to 55 μm is generated between the narrowest portion and the widest portion in the gap between the quartz-based PLCs 3001 and 3002. A difference of about 12 μm is generated between the narrowest part and the widest part in the gap between the optical waveguide port of the quartz-based PLC3001 and the optical waveguide port of the quartz-based PLC 3002.

In another aspect of , in this embodiment, since the x-axis direction interval between the cores 3011 of the optical waveguide array is set to 20 μm, the x-axis direction interval between the two ends of the optical waveguide array becomes 140 μm and thus the difference between the narrowest and widest portions of the gap between the optical waveguide port of the quartz-based PLC3001a and the optical waveguide port of the quartz-based PLC3002 a is about 1 μm.

By adopting the above-described structure, in this embodiment, when the quartz-based PLCs 3001a and 3002a are mounted on the quartz-based substrate 3003, the positions of the cores 3011 in the two quartz-based PLCs 3001a and 3002a are aligned on the same line, and low-loss connection of light can be achieved. Thus, in this embodiment, a simple multi-chip mounting can be achieved with sub-micron accuracy by passive alignment mounting without input/output of light.

Further, in this embodiment, the pitch conversion sections 3014 and 3015 are provided near the connection end faces 11 and 12 of the quartz-based PLCs 3001a and 3002 a. This makes it possible to reduce an increase in loss and a variation in loss between optical waveguide ports due to an axis deviation and a gap expansion between the quartz-based PLCs 3001 and 3002 caused by an angle error of the connection end faces 11 and 12, and reduce an influence of the angle error of the connection end faces 11 and 12.

Note that in this embodiment, an example has been described in which the quartz glass layer 3012 of the quartz-based substrate 3003 is manufactured by the same process as that of the optical waveguide layer 3008 of the quartz-based PLCs 3001a and 3002a, however, the quartz glass layer 3012 may be manufactured by other manufacturing methods, for example, even the same effect as described above may be obtained by V-groove processing or processing using cutting or the like or laser processing as long as the fitting grooves 3007 and 3013 by can be formed.

Further, in this embodiment, the quartz-based PLCs 3001a and 3002a are only placed on the quartz-based substrate 3003 in a form in which they are supported by the spacer fiber 3006, but are not fixed. In this way, the quartz-based PLCs 3001a and 3002a can be detached from the quartz-based substrate 3003, and pluggable connections can be achieved, in which the necessary quartz-based PLCs 3001a and 3002a can be connected only when necessary, like connectors. As mentioned above, this form is called PPCP.

In cases, the quartz-based PLCs 3001a and 3002a can be secured to the quartz-based substrate 3003 by filling the gap between the quartz-based PLC 3003 and the quartz-based PLCs 3001a and 3002a with an optical adhesive having a matched index of refraction alternatively, of the two quartz-based PLCs 3001a and 3002a can be secured to the quartz-based substrate 3003 and the other can be detachable.

[ seventh embodiment ]

Next, a seventh embodiment of the present invention will be described. Fig. 10A and 10B are schematic views showing a connection structure of an optical waveguide chip according to a seventh embodiment of the present invention, and in fig. 10A and 10B, the same reference numerals as in fig. 7A to 7D, 8A, 8B, 9A, and 9B denote the same components. Fig. 10A is a perspective view of the connection structure of the optical waveguide chip, and fig. 10B is a plan view of the connection structure as viewed from the upper side.

In the quartz-based PLCs 3001b and 3002b according to this embodiment, the cutouts 13 and 14 are added to the corners of the connection end faces (entrance/exit end faces) 11b and 12b in the quartz-based PLCs 3001a and 3002a according to the sixth embodiment so that the relative areas of the connection end faces 11b and 12b become small.

In this embodiment, the following effects can be obtained by adding the cuts 13 and 14. In the sixth embodiment, the interval between the cores 3011 of the optical waveguide array in the connection end faces 11 and 12 is narrowed, so that the difference in the gap between the quartz-based PLCs 3001a and 3002a caused by the angle error of the connection end faces 11 and 12 is relatively small. However, if the angle error of the connection end faces 11 and 12 in the substrate plane (in the sheet surface of fig. 9B) is 0.4 ° with respect to the design value, there is still a difference of about 50 μm between the narrowest portion and the widest portion in the gap between the quartz-based PLCs 3001a and 3002 a.

On the other hand, , in this embodiment, the cutouts 13 and 14 are provided on the connection end faces 11b and 12b with respect to the x-axis direction width of 8mm in the quartz-based PLCs 3001a and 3002a so that the x-axis direction widths of the connection end faces 11b and 12b of the quartz-based PLCs 3001b and 3002b become smaller, i.e., 4mm, thereby processing each of the quartz-based PLCs 3001a and 3002a into a hexagonal shape in a plan view.

In this embodiment, for the gap between the quartz-based PLCs 3001b and 3002b, the relative gap difference can be made small by the pitch converting portions 3014 and 3015, and further, the absolute gap difference can be made small by the cutouts 13 and 14. as a result, the connection loss between the quartz-based PLCs 3001b and 3002b can be reduced, and the loss difference between the optical waveguide ports can be reduced by steps.

The cuts 13 and 14 may be formed by cutting. Further, any of the cuts 13 and 14 may be provided using a laser cutting technique or the like. Further, it can be easily seen that the shape and angle of the cutouts 13 and 14 can be arbitrarily set if the effects of the embodiment can be obtained.

Regarding the pitch converting portions 3014 and 3015, in the example shown in fig. 9B and 10B, the cores 3011 of the optical waveguide array are concentrated on the center, and the cores 3011 are arranged so as to be symmetrical with respect to the center line of the quartz-based PLCs 3001B and 3002B (3001a and 3002a) in the optical axis direction (z-axis direction). However, the pitch conversion sections 3014 and 3015 may have any layout. As shown in the plan view of fig. 11, the core 3011 may be arranged asymmetrically with respect to the center lines of the quartz-based PLCs 3001b and 3002b (3001a and 3002a) in the optical axis direction.

Further, it is not always necessary to arrange the connection end faces 11b and 12b at the centers of the quartz-based PLCs 3001b and 3002b the pitch conversion portions 3014 and 3015 may be provided near the side end portions among the ends in the x-axis direction of the quartz-based PLCs 3001b and 3002b, and cutouts may be provided in the quartz-based PLCs 3001b and 3002b to leave the ends as connection end faces, that is, cutouts may be provided only at the side corners in the x-axis direction of the connection end faces 11b and 12 b.

Further, the number of optical waveguide chips is not always limited to the connection of two chips, and three optical waveguide chips may be mounted by the PPCP technique, or four optical waveguide chips may be mounted by the PPCP technique, as shown in FIG. 12. FIG. 12 is a plan view showing a connection structure with four quartz-based PLCs 3001b, 3002b, 3016 and 3017 mounted on a quartz-based substrate 3003b, as viewed from the upper side.

The structure of each of the quartz-based PLCs 3001b and 3002b is the same as described above.A quartz-based PLC 3016 corresponds to the structure obtained by rotating the quartz-based PLC3002 b by 90 DEG in the plane of the substrate.A pitch conversion part 3018 and a notch 15 of a connection end face with the quartz-based PLC 3017 are formed on the quartz-based PLC 3016.A pitch conversion part 3019, notches 16 provided on the connection end face with the quartz-based PLC3001b and the connection end face with the quartz-based PLC 3016, and notches 17 provided on the connection end face with the quartz-based PLC3002 b and the connection end face with the quartz-based PLC 3016 are formed on the quartz-based PLC 3017.

By the structure shown in fig. 12, a trifurcated waveguide connection structure can be realized. In the sixth and seventh embodiments, only examples of simple waveguide connections are shown. However, any optically functional structure may be integrated. For example, a switch, a wavelength multiplexer/demultiplexer, a polarization integration function, a Mach-Zehnder (Mach-Zehnder) interference circuit, a ring resonator, a phase adjustment circuit, or the like may be provided. Alternatively, a laser, a photodiode, or the like including a waveguide mechanism may be provided. In addition, a waveguide having a large nonlinear effect can be used.

[ eighth embodiment ]

Next, an eighth embodiment of the present invention will be described. Fig. 13 is a plan view showing a connection structure of an optical waveguide chip according to an eighth embodiment of the present invention, and in fig. 13, the same reference numerals as in fig. 7A to 7D, fig. 8A, fig. 8B, fig. 9A and 9B, fig. 10A, fig. 10B, and fig. 11 denote the same components.

The quartz-based PLCs 3001c and 3002c according to this embodiment have the same structure as the quartz-based PLCs 3001b and 3002b according to the seventh embodiment, except for the shape of the fitting groove 3007 c. The quartz base substrate 3003c has the same structure as the quartz base substrate 3003 except for the shape of the fitting groove 3013 c.

Fig. 14A and 14B are plan views showing the shapes of the fitting grooves 3007c and 3013 c. The fitting grooves 3007c each have such a shape as follows: the longitudinal direction is parallel to the z-axis direction (the optical axis direction and the left-right direction of fig. 13, 14A, and 14B), and the width in the x-axis direction (the direction perpendicular to the optical axis direction in the substrate plane) changes along the longitudinal direction.

The width of the narrowest portion of the central portions of the fitting grooves 3007c is set so that it is in contact with the spacer fiber 3006 when the spacer fiber 3006 is fitted in the fitting grooves 3007c the central portions facilitate alignment of the quartz-based PLCs 3001c and 3002c in the in-plane direction when fitting, and further , the width of the fitting grooves 3007c other than the central portions is smaller than the width of the spacer fiber 3006 and becomes larger as the point is farther from the central portions in the longitudinal direction, and further, the length of the fitting grooves 3007c is set longer than the spacer fiber 3006.

The fitting groove 3013c formed in the quartz glass layer 3012 of the quartz base substrate 3003c is formed in the same shape as the fitting groove 3007c at a position facing the fitting groove 3007c when the quartz base PLCs 3001c and 3002c are mounted on the quartz base substrate 3003 c.

Changing the fitting grooves to the shapes of the fitting grooves 3007c and 3013c can be easily achieved by changing the photolithography mask.

When the fitting grooves 3007c and 3013c are formed, in this embodiment, the following remarkable effects can be obtained. If the angle errors of the connection end faces 11b and 12b of the quartz-based PLCs 3001c and 3002c in the substrate plane are small, the spacer fibers 3006 are fitted in the fitting grooves 3007c and 3013c so that the longitudinal direction of the spacer fibers 3006 becomes parallel to the longitudinal direction of the fitting grooves 3007c and 3013c, as shown in fig. 14A.

In another aspect, if the angle error of the connection end faces 11b and 12b of the quartz-based PLCs 3001c and 3002c in the substrate plane is large, fine adjustments can be made to make the angle error of the connection end faces 11b and 12b smaller, more specifically, after the quartz-based PLCs 3001c and 3002c are mounted on the quartz-based base 3003c, at least of the two quartz-based PLCs 3001c and 3002c are rotated in the substrate surface so that the gap between the quartz-based PLCs 3001c and 3002c becomes smaller.

With the above-described structure, each of the spacer fibers 3006 is fitted in the corresponding fitting grooves 3007c and 3013c at the center of the fitting grooves 3007c and 3013 c. At a portion away from the center, there is a gap between the fitting grooves 3007c and 3013c and the spacer fiber 3006. Thus, the quartz-based PLCs 3001c and 3002c can rotate in the plane of the substrate. In the example shown in fig. 14B, the quartz-based PLC3002 c is rotated to make the gap between the quartz-based PLCs 3001c and 3002c smaller.

As described above, in this embodiment, the passive alignment mounting described in the sixth and seventh embodiments can be achieved. Further, even if there is an angle error of the connection end face, it is possible to reduce the influence as much as possible, and to reduce an increase in loss due to an axis deviation and a gap expansion between the quartz-based PLCs 3001c and 3002c and a variation in loss between optical waveguide ports.

[ ninth embodiment ]

Next, a ninth embodiment of the present invention will be described. Fig. 15A and 15B are plan views showing the shapes of the fitting grooves of the optical waveguide chip and the quartz-based substrate according to the ninth embodiment of the present invention, and in fig. 15A and 15B, the same reference numerals as in fig. 13, 14A and 14B denote the same parts.

The quartz-based PLCs 3001d and 3002d according to this embodiment have the same structure as the quartz-based PLCs 3001c and 3002c according to the eighth embodiment, except for the shape of the fitting groove 3007 d. The quartz base substrate 3003d has the same structure as the quartz base substrate 3003c except for the shape of the fitting groove 3013 d.

In each fitting groove 3007d, the longitudinal direction is parallel to the z-axis direction, and the x-axis direction width of the narrowest portion at the central portion is a width corresponding to the spacing fiber 3006, and the width becomes larger as the point is farther from the central portion in the longitudinal direction, as is the fitting groove 3007 c.

The fitting groove 3013d formed in the quartz glass layer 3012 of the quartz base substrate 3003d is formed in the same shape as the fitting groove 3007d at a position facing the fitting groove 3007d when the quartz-based PLCs 3001d and 3002d are mounted on the quartz base substrate 3003 d.

Therefore, after the quartz-based PLCs 3001d and 3002d are mounted on the quartz-based substrate 3003d as in the eighth embodiment, at least of the two quartz-based PLCs 3001d and 3002d can be rotated in the substrate surface so that the gap between the quartz-based PLCs 3001d and 3002d becomes small, and the effect described in the eighth embodiment can be obtained (fig. 15B).

The fitting groove 3007d and the fitting groove 3007c are different in that both ends in the longitudinal direction have an arc shape in plan view. That is, the arc shape has a predetermined distance from the center of the fitting groove 3007d in the substrate plane. The distance in the substrate plane between the arcs of both end portions in the longitudinal direction is set so that both end portions of the fitting groove 3007d are in contact with both end portions of the spacer fiber 3006 when the spacer fiber 3006 is fitted in the fitting groove 3007 d.

The length of the fitting groove 3007c described in the eighth embodiment is set to be longer than the spacer fiber 3006. Thus, there is a fear that: when the quartz-based PLCs 3001c and 3002c rotate in the plane of the substrate, the positions of the quartz-based PLCs 3001c and 3002c in the z-axis direction are shifted.

On the other hand , in this embodiment, both ends of each fitting groove 3007d always contact the spacer fiber 3006 when the spacer fiber 3006 is fitted in the fitting grooves 3007d, so that even after the quartz-based PLCs 3001d and 3002d are mounted on the quartz-based substrate 3003d, the positions of the quartz-based PLCs 3001d and 3002d in the z-axis direction are not shifted and more precise passive alignment mounting can be performed, even if the quartz-based PLCs 3001d and 3002d are rotated in the substrate plane.

However, based on the resolution of the photolithography, every of the fitting grooves 3007d and 3013d are formed into a polygonal shape in a plan view, so that a pseudo-arc shape in which the distance from the center of the fitting groove 3007d or 3013d in the substrate plane is almost constant is obtained, thereby obtaining an effect equivalent to the perfect arc shape.

Note that examples of applying the eighth and ninth embodiments to the seventh embodiment have been described with respect to fig. 13, 14A, 14B, 15A, and 15B. However, of course, these embodiments may be applied to the sixth embodiment.

In the sixth to ninth embodiments, a Planar Lightwave Circuit (PLC) of a thin glass film formed on a silicon substrate has been described as an optical waveguide chip by way of example. However, the present invention can be applied to any optical waveguide chip including a waveguide mechanism. For example, as a material of the substrate or the optical waveguide, quartz, a polymer made of an organic substance, a semiconductor or compound semiconductor waveguide using Si, silicon nitride (SiN), gallium arsenide, indium phosphide (InP), or the like, and a dielectric such as Lithium Niobate (LN), Periodically Polarized Lithium Niobate (PPLN), or Lithium Tantalate (LT) can be used in addition to quartz glass.

In the sixth to ninth embodiments, each PLC has two or more fitting grooves 3007, 3007c, or 3007 d. The fitting grooves 3013, 3013c, or 3013d formed in the quartz-based substrate 3003, 3003c, or 3003d need only be provided in number according to the fitting grooves 3007, 3007c, or 3007 d. The spacer fibers 3006 need only be provided in a number corresponding to the number of assembly slots 3007, 3007c, 3007d, 3013c, or 3013 d.

Further, in the sixth to ninth embodiments, examples have been described in which the fitting grooves 3007, 3007c, 3007d, 3013c, and 3013d are grooves each having a rectangular cross section. However, grooves whose groove widths are narrowed toward the substrates 3009, 3003c, and 3003d, for example, grooves each having a V-shaped or W-shaped cross section or grooves each having a U-shaped cross section, may be used.

In the sixth to ninth embodiments, the height of the spacer fiber 3006 is preferably larger than the sum of the depth of the fitting grooves 3013, 3013c, and 3013d on the substrate side and the depth of the fitting grooves 3007, 3007c, and 3007d on the optical waveguide chip side. This may provide a gap between the substrate and the optical waveguide chip.

Further, in the sixth to ninth embodiments, the cylindrical spacer fiber 3006 is used as the spacer member. However, the present invention is not limited thereto. The material of the spacer member may be any material, for example, an inorganic substance such as glass, metal, or polymer. Further, the shape is not limited as long as it can be appropriately fitted in the fitting groove 3007, 3007c, 3007d, 3013c, or 3013 d. That is, the spacing member may have a cylindrical shape, a parallelepiped shape, a spherical shape, or the like. Further, if the height of the spacer member is changed when the spacer member is fitted in the fitting groove, the optical waveguide chip may be inclined with respect to the substrate. Therefore, the material, size and shape of the spacer member are preferably set so that the height thereof is difficult to change when the spacer member is fitted in the fitting groove.

[ tenth embodiment ]

In the quartz-based PLC or quartz-based graph 22 including a Si substrate used in PPCP, a signal derived from Si and SiO is generated in many cases₂The difference in thermal expansion coefficient therebetween, and warpage occurs. Such warping is sometimes problematic even for normal application purposes of the PLC, and is particularly problematic in the case of PPCP that requires passive alignment mounting. In many cases, the optical connection between PLCs is deviated, resulting in an increase in insertion loss. In addition, the PPCP may be used for an optical waveguide integrating a multilayer structure. At this time, the PLC is sometimes thinned by polishing. With this polishing, warpage tends to be greater than in a PLC of typical thickness.

Therefore, the warpage caused by the difference between the thermal expansion coefficients of the materials affects the thinning and passive alignment performed for the size reduction and the simple connection (which are characteristics of the PPCP), and excessive insertion loss occurs.

The tenth to fifteenth embodiments of the present invention are directed to alleviating the warpage caused by the physical property value and suppressing the increase of the optical connection loss while maintaining the accurate and simple mounting method.

Fig. 16A to 16D are schematic views showing a connection structure of an optical waveguide chip according to a tenth embodiment of the present invention. Fig. 16A is a perspective view of a connection structure of an optical waveguide chip, fig. 16B is an exploded view of parts of the connection structure, fig. 16C is a diagram showing a bonding surface of the optical waveguide chip to a substrate, and fig. 16D is a sectional view of the connection structure taken along the xy plane. In fig. 16A to 16D, a total of seven members, that is, quartz-based PLCs 101 and 102, which are two optical waveguide chips each formed of a quartz-based glass layer including a Si substrate and an optical waveguide layer, a base 103, which is manufactured by the same method as the quartz-based PLCs 101 and 102 and does not include a waveguide, and four spacer fibers 106 (spacer members), are combined, thereby forming a PPCP.

As shown in fig. 16A, an input optical signal 105 that has entered the quartz-based PLC102 propagates through the optical waveguide layer of the quartz-based PLC102, exits the quartz-based PLC102 and enters the quartz-based PLC101, propagates through the optical waveguide layer of the quartz-based PLC101, and exits the quartz-based PLC101 as an output optical signal 104.

As shown in fig. 16D, the quartz-based PLC101 has such a structure: wherein an optical waveguide layer 109 configured to transmit input signal light 105 is formed on a supporting substrate 110 made of Si. The optical waveguide layer 109 is formed of a cladding layer 111 and a core layer 112, and the cladding layer 111 is formed of SiO₂To make, the core 112 is formed in the clad layer 111 and made of SiO containing a dopant₂Further, fitting grooves 107 are formed in the cladding layer 111 the structure of the quartz-based PLC102 is the same as that of the quartz-based PLC101 FIG. 16C shows the junction surfaces of the optical waveguide layers 109 (cladding layer 111) and the substrate 103 of the quartz-based PLCs 101 and 102, it is apparent from FIG. 16C that two fitting grooves 107 are formed in PLCs.

As shown in fig. 16A and 16B, the quartz-based PLC101 and the quartz-based PLC102 are arranged side by side such that the connection end faces 11 and 12 face each other. Two quartz-based PLCs 101 and 102 are mounted on a substrate 103.

A glass layer 114 made of the same material as the clad layers 111 of the quartz-based PLCs 101 and 102 is formed on the surface of the base 103 where the quartz-based PLCs 101 and 102 are mounted, of the support substrate 113 made of Si. In the glass layer 114 (cladding layer), a fitting groove 115 having the same shape as the fitting groove 107 is formed at a position facing the fitting groove 107 of the quartz-based PLCs 101 and 102 when the quartz-based PLCs 101 and 102 are mounted on the substrate 103.

FIG. 16C shows the interface of the glass layer 114 with the quartz-based PLCs 101 and 102. As described above, since two fitting grooves 107 are formed in PLCs, a total of four fitting grooves 115 are formed in the glass layer 114, namely, two fitting grooves 115 formed at positions facing the fitting grooves 107 of the quartz-based PLC101 and two fitting grooves 115 formed at positions facing the fitting grooves 107 of the quartz-based PLC 102. in this embodiment, the longitudinal directions of the fitting grooves 107 and 115 are set to be parallel to the z-axis direction (the optical axis direction of light exiting from the quartz-based PLC102 to the quartz-based PLC101 and the optical axis direction of light entering the quartz-based PLC101 or the left-right direction of FIGS. 16A to 16C).

Further, in the glass layer 114, a warp reducing groove 108 is formed for the purpose of reducing warp of the substrate 103. The warpage reducing groove 108 is formed to a position reaching the support substrate 113 so that the support substrate 113 is exposed to the bottom of the warpage reducing groove 108. When the glass layer 114 is cut until the support substrate 113 is exposed, the effect of reducing the warpage of the base 103 can be maximized. In this embodiment, the warpage reducing groove 108 is formed to extend from a position facing the quartz-based PLC101 to a position facing the quartz-based PLC102 along the z-axis direction.

To manufacture the PPCP according to this embodiment, the spacer fibers 106 are respectively fitted in four fitting grooves 115 formed in the glass layer 114 of the substrate 103. Then, the two spacer fibers 106 fitted in the fitting grooves 115 of the glass layer 114 are fitted in the two fitting grooves 107 formed in the optical waveguide layer 109 of the quartz-based PLC101 so that the bonding surface of the glass layer 114 and the bonding surface of the optical waveguide layer 109 (cladding layer 111) of the quartz-based PLC101 face each other, as shown in fig. 16B, that is, so that the support substrate 110 is located at the upper side and the optical waveguide layer 109 is located at the lower side, thereby mounting the quartz-based PLC101 on the substrate 103.

Similarly, the two spacer fibers 106 fitted in the fitting grooves 115 of the glass layer 114 are fitted in the two fitting grooves 107 formed in the optical waveguide layer 109 of the quartz-based PLC102 such that the bonding surface of the glass layer 114 and the bonding surface of the optical waveguide layer 109 of the quartz-based PLC102 face each other, thereby mounting the quartz-based PLC102 on the substrate 103.

In this way, the quartz-based PLCs 101 and 102 may be mounted on the substrate 103 such that the connection end surfaces 11 and 12 of the quartz-based PLCs 101 and 102 closely face each other, and optical connection between the quartz-based PLCs 101 and 102 may be achieved.

The fitting grooves 107 and 115 and the warp-alleviating groove 108 are formed by photolithography. Therefore, the width (dimension in the left-right direction of fig. 16D), the length (dimension in the left-right direction of fig. 16B and 16C), and the position of the fitting grooves 107 and 115 can be determined with very high accuracy. Accordingly, the axial deviation of the optical waveguide layer 109 in the direction in the substrate plane can be aligned with very high accuracy.

Further, the spacer fibers 106 having the same diameter are fitted in the four fitting grooves 115 of the substrate 103 side, the fitting grooves 107 of the quartz-based PLC101 side are fitted on two of the four spacer fibers 106, and the fitting grooves 107 of the quartz-based PLC102 side are fitted on the remaining two spacer fibers 106. Thus, the tilt of the quartz-based PLCs 101 and 102 with respect to the substrate 103 can be made small enough to be negligible.

When the above-described PPCP structure is adopted, the core positions in the two quartz-based PLCs 101 and 102 with respect to the substrate 103 are determined with high accuracy. When the quartz-based PLCs 101 and 102 are mounted on the substrate 103, the positions of the cores 112 in the two quartz-based PLCs 101 and 102 are aligned on the same line, and low loss connection of light can be achieved. Thus, in this embodiment, a simple multi-chip mounting can be achieved with sub-micron accuracy by passive alignment mounting without input/output of light. The reduction in size of the optical circuit can also be achieved by implementing the integration of the PLCs 101 and 102.

Further, in this embodiment, since the warp reducing groove 108 reaching the support substrate 113 is formed in the glass layer 114 of the base 103, it is possible to reduce the warp of the base 103 caused by the difference in thermal expansion coefficient between the support substrate 113 made of Si and the glass layer 114, and to suppress the increase in optical connection loss due to the axial deviation and the gap expansion between the quartz-based PLCs 101 and 102 caused by the warp of the base 103.

Tenth example 1

Next, a tenth embodiment of the present invention will be described, fig. 17A to 17D are schematic diagrams showing a connection structure of an optical waveguide chip according to a tenth embodiment of the present invention, fig. 17A is a perspective view of the connection structure of the optical waveguide chip, fig. 17B is an exploded view of parts of the connection structure, fig. 17C is a diagram showing a bonding surface of the optical waveguide chip to a substrate, and fig. 17D is a sectional view of the connection structure taken along the xy plane.

As shown in fig. 17A, an input optical signal 205 that has entered the quartz-based PLC202 propagates through the optical waveguide layer of the quartz-based PLC202, exits the quartz-based PLC202 and enters the quartz-based PLC201, propagates through the optical waveguide layer of the quartz-based PLC201, and exits the quartz-based PLC201 as an output optical signal 204.

Like the quartz-based PLC101, the quartz-based PLC201 has such a structure: wherein an optical waveguide layer 209 configured to transmit input signal light 205 is formed on a support substrate 210 made of Si. The optical waveguide layer 209 is formed of a cladding layer 211 and a core portion 212, and the cladding layer 211 is formed of SiO₂As a result, the core 1011 is formed in the cladding 1010. Like the quartz-based PLC101, a fitting groove 207 is formed in the cladding layer 211.

In addition, in the clad layer 211, a warpage reducing groove 208 is formed for the purpose of reducing warpage of the quartz-based PLC 201. Each warpage reducing groove 208 is formed to a position reaching the support substrate 210 such that the support substrate 210 is exposed to the bottom of the warpage reducing groove 208. When the clad layer 211 is cut until the support substrate 210 is exposed, the effect of reducing the warpage of the quartz-based PLC201 can be maximized.

Further, in this embodiment, the longitudinal direction of the fitting groove 207 and the longitudinal direction of the warpage reducing groove 208 are set to be parallel to the z-axis direction (the optical axis direction of the light exiting from the quartz-based PLC202 to the quartz-based PLC201 and the optical axis direction of the light entering the quartz-based PLC201 or the left-right direction of fig. 17A to 17C). The warpage reducing groove 208 is arranged so as not to intersect with the core 212 of the optical waveguide layer 209 and not to obstruct light transmission in the optical waveguide layer 209.

The structure of the quartz-based PLC202 is the same as that of the quartz-based PLC201 in this embodiment, two fitting grooves 207 and two warpage reducing grooves 208 are formed in PLCs.

A glass layer 214 made of the same material as the clad layer 211 of the quartz-based PLCs 201 and 202 is formed on the surface of the support substrate 213 made of Si in the base 203 where the quartz-based PLCs 201 and 202 are mounted. In the glass layer 214, a fitting groove 215 having the same shape as the fitting groove 207 is formed at a position facing the fitting groove 207 of the quartz-based PLCs 201 and 202 when the quartz-based PLCs 201 and 202 are mounted on the substrate 203.

To manufacture the PPCP according to this embodiment, spacer fibers 206 (spacer members) are respectively fitted in four fitting grooves 215 formed in a glass layer 214 of a substrate 203. Then, the two spacer fibers 206 fitted in the fitting grooves 215 of the glass layer 214 are fitted in the two fitting grooves 207 formed in the optical waveguide layer 209 of the quartz-based PLC201 so that the bonding surface of the glass layer 214 and the bonding surface of the optical waveguide layer 209 (cladding layer 211) of the quartz-based PLC201 face each other, thereby mounting the quartz-based PLC201 on the substrate 203.

Similarly, the two spacer fibers 206 fitted in the fitting grooves 215 of the glass layer 214 are fitted in the two fitting grooves 207 formed in the optical waveguide layer 209 of the quartz-based PLC202 such that the bonding surface of the glass layer 214 and the bonding surface of the optical waveguide layer 209 of the quartz-based PLC202 face each other, thereby mounting the quartz-based PLC202 on the substrate 203.

In this way, the quartz-based PLCs 201 and 202 can be mounted on the substrate 203 such that the connection end face 21 of the quartz-based PLC201 and the connection end face 22 of the quartz-based PLC202 closely face each other, and the simple optical connection with the accuracy of the submicron order and the size reduction of the optical circuit described in the tenth embodiment can be achieved.

Further, in this embodiment, since the warpage reducing grooves 208 reaching the support substrate 210 are formed in every optical waveguide layers 209 in the quartz-based PLCs 201 and 202, it is possible to reduce warpage of the quartz-based PLCs 201 and 202 caused by a difference in thermal expansion coefficient between the support substrate 210 made of Si and the optical waveguide layer 209 (cladding layer 211), and to suppress an increase in optical connection loss due to axial deviation and gap expansion between the quartz-based PLCs 201 and 202 caused by warpage of the quartz-based PLCs 201 and 202.

[ twelfth embodiment ]

Next, a twelfth embodiment of the invention will be described. Fig. 18 is a sectional view showing a connection structure of an optical waveguide chip according to a twelfth embodiment of the present invention.

Like the quartz-based PLC201, the quartz-based PLC301 has such a structure: in which an optical waveguide layer 309 is formed on a support substrate 310 made of Si. The optical waveguide layer 309 is formed of a cladding layer 311 and a core layer 312, the cladding layer 311 being formed of SiO₂As a result, the core 1011 is formed in the cladding 1010. A fitting groove 307 similar to the fitting grooves 107 and 207 and a warpage reducing groove 308 similar to the warpage reducing groove 208 are formed in the cladding layer 311.

A glass layer 314 made of the same material as the clad layer 311 is formed on the surface of the base 303 made of Si supporting the substrate 313 where the quartz-based PLC301 is mounted. In the glass layer 314, a fitting groove 315 having the same shape as the fitting groove 307 is formed at a position facing the fitting groove 307 of the quartz-based PLC301 when the quartz-based PLC301 is mounted on the substrate 303. Further, a warp reducing groove 316 similar to the warp reducing groove 108 is formed.

The method of mounting the quartz-based PLCs 301 on the substrate 303 using the spacer fibers 306 (spacer members) is the same as that in the tenth and tenth embodiments, and the description thereof will be omitted although fig. 18 shows only quartz-based PLCs 301, the connection method of a plurality of quartz-based PLCs is also the same as that described in the tenth and tenth embodiments.

In this embodiment, in addition to the arrangements described in the tenth and tenth embodiments, the warpage-reducing grooves 308 and 316 formed in the cladding layer 311 and the glass layer 314 are filled with the filler materials 317 and 318, in which the thermal expansion coefficients of the filler materials 317 and 318 and the constituent Substances (SiO) of the cladding layer 311 and the glass layer 314₂) Are different.

Therefore, in this embodiment, it is possible to alleviate the warpage of the quartz-based PLC301 and the substrate 303 and suppress the increase in the optical connection loss due to the shaft deviation and the gap expansion between the two PLCs (only of which are shown in FIG. 18.) at the same time, it is possible to prevent dust and the like from accumulating in the warpage-alleviating grooves 308 and 316 and achieve satisfactory engagement of the PPCP.

As the filler 317 and 318, a constituent Substance (SiO) having a lower hardness than the clad layer 311 and the glass layer 314 is used₂) The hardness of (3). An example of such a substance is silicone.

Further, as the filler 317 and 318, a constituent Substance (SiO) having a higher thermal expansion coefficient than the clad layer 311 and the glass layer 314 can be used₂) The coefficient of thermal expansion of (1). An example of such a substance is silicon (Si).

However, the present invention is not limited thereto, and the warp mitigation groove may be filled with a filling material when the warp mitigation groove exists only on the substrate side as in the tenth embodiment.

[ thirteenth embodiment ]

Next, a thirteenth embodiment of the invention will be described. Fig. 19A to 19D are schematic views showing a connection structure of an optical waveguide chip according to a thirteenth embodiment of the present invention. Fig. 19A is a perspective view of a connection structure of optical waveguide chips, fig. 19B is an exploded view of parts of the connection structure, fig. 19C is a diagram showing bonding faces of three optical waveguide chips, and fig. 19D is a sectional view of the connection structure taken along the xy plane.

In the tenth to twelfth embodiments, a quartz-based PLC (optical waveguide chip) is mounted on a substrate without an optical waveguide layer. In this embodiment, an example of mounting a plurality of other quartz-based PLCs on the quartz-based PLC will be described.

As shown in fig. 19A, an input optical signal 405 that has entered the quartz-based PLC402 propagates through the optical waveguide layer of the quartz-based PLC402, exits the quartz-based PLC402 and enters the quartz-based PLC401, propagates through the optical waveguide layer of the quartz-based PLC401, and exits the quartz-based PLC401 as an output optical signal 404. Further, the input optical signal 420 that has entered the quartz-based PLC403 propagates through the optical waveguide layer of the quartz-based PLC403 and exits the quartz-based PLC403 as an output optical signal 419.

Like the quartz-based PLC101, the quartz-based PLC401 has a structure in which: wherein an optical waveguide layer 409 configured to transmit input signal light 405 is formed on a support substrate 410 made of Si. The optical waveguide layer 409 is formed of a cladding layer 411 and a core part 412, and the cladding layer 411 is formed of SiO₂As a result, the core 1011 is formed in the cladding 1010. Like the quartz-based PLC101, a mounting groove 407 is formed in the cladding 411.

In addition, in the cladding layer 411, a warpage reducing groove 408 is formed for the purpose of reducing warpage of the quartz-based PLC 401. The depth D1 of the fitting groove 407 is 5 μm, and the depth D2 of the warpage-reducing groove 408 is 15 μm. The depth D2 need only be 1 μm or more. In this embodiment, each warp mitigation groove 408 is formed to a position reaching the support substrate 410 such that the support substrate 410 is exposed to the bottom of the warp mitigation groove 408. When the clad 411 is cut until the support substrate 410 is exposed, the effect of reducing the warpage of the quartz-based PLC401 can be maximized. The interval D3 between the fitting groove 407 and the warpage-reducing groove 408 is 70 μm. The spacing D3 need only be 1 μm or more.

In this embodiment, the longitudinal direction of the fitting groove 407 and the longitudinal direction of the warpage reducing groove 408 are set to be parallel to the z-axis direction (the optical axis direction of the light exiting from the quartz-based PLC402 to the quartz-based PLC401 and the optical axis direction of the light entering the quartz-based PLC401 or the left-right direction of fig. 19A to 19C). The quartz-based PLC401 is designed with a higher priority in consideration of warpage mitigation than in reduction of transmission loss of an optical signal. That is, as shown in fig. 19C, the shape of the warp alleviating groove 408 includes not only a portion extending in the z-axis direction but also a portion extending in the x-axis direction (a direction perpendicular to the optical axis direction in the substrate plane), and the portion extending in the x-axis direction divides the optical waveguide layer 409.

Fig. 20 shows a structure of the PPCP in which the optical waveguide layer 409 is divided, fig. 20 is a sectional view of the PPCP taken along the yz plane fig. 20a light beam that has exited from the core 412 on the side of the optical waveguide layer 409 divided by the warp reducing groove 408 enters the core 412 on the other side across the warp reducing groove 408, and therefore, in this embodiment, the transmission loss of an optical signal is increased as described above, however, since the warp reducing groove 408 is provided not only in the z-axis direction but also in the x-axis direction, the warp of the quartz-based PLC401 can be more effectively suppressed, the structure of the quartz-based PLC402 is the same as that of the quartz-based PLC 401.

The quartz-based PLC403 has such a structure: wherein an optical waveguide layer 415 configured to transmit an input signal light 420 is formed on a support substrate 413 made of Si. The optical waveguide layer 415 is formed of a cladding layer 414 and a core 416, and the cladding layer 414 is formed of SiO₂As a result, the core 416 is formed in the cladding 414. In the cladding 414, a fitting groove 417 having the same shape as the fitting groove 407 is formed at a position facing the fitting groove 407 of the quartz-based PLCs 401 and 402 when the quartz-based PLCs 401 and 402 are mounted on the quartz-based PLC 403.

In addition, in the clad layer 414, a warpage reducing groove 418 is formed for the purpose of reducing warpage of the quartz-based PLC 403. The depth D1 of the fitting groove 417 is 5 μm and the depth D2 of the warpage-reducing groove 418 is 15 μm as in the quartz-based PLCs 401 and 402. As described above, the depth D2 need only be 1 μm or more. Each warpage reducing groove 418 is formed to a position reaching the support substrate 413 such that the support substrate 413 is exposed to the bottom of the warpage reducing groove 418. When the clad layer 414 is cut until the support substrate 413 is exposed, the effect of reducing the warpage of the quartz-based PLC403 can be maximized. Further, the interval D3 between the fitting groove 417 and the warpage-reducing groove 418 was 70 μm. The spacing D3 need only be 1 μm or more.

In this embodiment, two warpage reducing grooves 418 are formed to extend from a position facing the quartz-based PLC401 to a position facing the quartz-based PLC402 along the z-axis direction. The warpage reducing groove 418 is arranged not to intersect the core 416 of the optical waveguide layer 415 and not to obstruct light transmission in the optical waveguide layer 415.

To manufacture the PPCP according to this embodiment, spacer fibers 406 (spacer members) are respectively fitted in four fitting grooves 417 formed in the cladding layer 414 of the quartz-based PLC 403. Then, the two spacer fibers 406 fitted in the fitting grooves 417 of the coating layer 414 are fitted in the two fitting grooves 407 formed in the optical waveguide layer 409 of the quartz-based PLC401 such that the bonding surface of the coating layer 414 and the bonding surface of the optical waveguide layer 409 (coating layer 411) of the quartz-based PLC401 face each other, thereby mounting the quartz-based PLC401 on the quartz-based PLC 403.

Similarly, the two spacer fibers 406 fitted in the fitting grooves 417 of the coating layer 414 are fitted in the two fitting grooves 407 formed in the optical waveguide layer 409 of the quartz-based PLC402 such that the coupling surface of the coating layer 414 and the coupling surface of the optical waveguide layer 409 of the quartz-based PLC402 face each other, thereby mounting the quartz-based PLC402 on the quartz-based PLC 403.

In this way, the quartz-based PLCs 401 and 402 can be mounted on the quartz-based PLC403 such that the connection end surface 41 of the quartz-based PLC401 and the connection end surface 42 of the quartz-based PLC402 closely face each other, and a simple optical connection with sub-micron accuracy and a reduction in size of an optical circuit can be achieved.

Further, in this embodiment, since the warpage reducing grooves 408 and 418 reaching the support substrates 410 and 413 are formed in the optical waveguide layers 409 and 415 of the quartz-based PLCs 401, 402 and 403, it is possible to reduce warpage of the quartz-based PLCs 401, 402 and 403 caused by a difference in thermal expansion coefficient between the support substrates 410 and 413 made of Si and the optical waveguide layers 409 and 415 (cladding layers 411 and 414), and to suppress an increase in optical connection loss due to axial deviation and gap expansion between the quartz-based PLCs 401 and 402 caused by warpage of the quartz-based PLCs 401, 402 and 403.

Note that the warpage-reducing grooves 408 and 418 according to this embodiment may be filled with the filling material described in the twelfth embodiment.

[ fourteenth embodiment ]

Next, a fourteenth embodiment of the invention will be described. Fig. 21A to 21D are schematic views showing a connection structure of an optical waveguide chip according to a fourteenth embodiment of the present invention. Fig. 21A is a perspective view of a connection structure of an optical waveguide chip, fig. 21B is an exploded view of parts of the connection structure, fig. 21C is a diagram showing bonding surfaces of three optical waveguide chips, and fig. 21D is a sectional view of the connection structure taken along the xy plane. This embodiment shows the best mode of the case where a plurality of other quartz-based PLCs are mounted on the quartz-based PLC.

As shown in fig. 21A, an input optical signal 505 that has entered the quartz-based PLC 502 propagates through the optical waveguide layer of the quartz-based PLC 502, exits the quartz-based PLC 502 and enters the quartz-based PLC501, propagates through the optical waveguide layer of the quartz-based PLC501, and exits the quartz-based PLC501 as an output optical signal 504. Further, the input optical signal 520 that has entered the quartz-based PLC503 propagates through the optical waveguide layer of the quartz-based PLC503 and exits from the quartz-based PLC503 as an output optical signal 519.

Like the quartz-based PLC401, the quartz-based PLC501 has a structure in which: wherein an optical waveguide layer 509 configured to transmit input signal light 505 is formed on a supporting substrate 510 made of Si. The optical waveguide layer 509 is formed of a cladding layer 511 and a core portion 512, the cladding layer 511 being formed of SiO₂As a result, the core 512 is formed in the clad 511. Like the quartz-based PLC401, a fitting groove 507 is formed in the clad layer 511. In addition, in the clad layer 511, a warpage reducing groove 508 is formed for the purpose of reducing warpage of the quartz-based PLC 501.

The depth D4 of both the fitting groove 507 and the warpage reducing groove 508 is 15 μm. The depth of the warpage-reducing groove 508 needs only to be 1 μm or more. In this embodiment, the fitting groove 507 and the warpage reducing groove 508 are formed to reach the position of the support substrate 510 so that the support substrate 510 is exposed to the bottoms of the grooves 507 and 508. When the clad layer 511 is cut until the support substrate 510 is exposed, the effect of reducing the warpage of the quartz-based PLC501 can be maximized. Further, the fitting groove 507 and the warpage reducing groove 508 are manufactured by a simultaneous process, thereby reducing the manufacturing cost. The interval D5 between the fitting groove 507 and the warp reducing groove 508 is 70 μm. The spacing D5 need only be 1 μm or more.

In this embodiment, the longitudinal direction of the fitting groove 507 and the longitudinal direction of the warpage reducing groove 508 are set to be parallel to the z-axis direction (the optical axis direction of the light exiting from the quartz-based PLC 502 to the quartz-based PLC501 and the optical axis direction of the light entering the quartz-based PLC501 or the left-right direction of fig. 21A to 21C). The quartz-based PLC501 is designed with a higher priority in consideration of reduction of transmission loss of an optical signal than warpage mitigation. That is, the two warpage reducing grooves 508 are arranged so as not to intersect the core portions 512 of the optical waveguide layer 509 and not to obstruct light transmission in the optical waveguide layer 509. The structure of the quartz-based PLC 502 is the same as that of the quartz-based PLC 501.

The quartz-based PLC503 has such a structure: wherein an optical waveguide layer 515 configured to transmit input signal light 520 is formed on a supporting substrate 513 made of Si. The optical waveguide layer 515 is formed of a cladding layer 514 and a core 516, and the cladding layer 514 is formed of SiO₂As a result, the core 516 is formed in the cladding 514. In the cladding 514, a fitting groove 517 having the same shape as the fitting groove 507 is formed at a position facing the fitting groove 507 of the quartz-based PLCs 501 and 502 when the quartz-based PLCs 501 and 502 are mounted on the quartz-based PLC 503. In addition, in the clad layer 514, a warpage reducing groove 518 is formed for the purpose of reducing warpage of the quartz-based PLC 503.

The depth D4 of both the fitting groove 517 and the warpage reducing groove 518 was 15 μm as in the quartz-based PLCs 501 and 502. The fitting groove 517 and the warpage reducing groove 518 are formed to a position reaching the support substrate 513 so that the support substrate 513 is exposed to the bottoms of the grooves 517 and 518. When the clad layer 514 is cut until the support substrate 513 is exposed, the effect of reducing the warpage of the quartz-based PLC503 can be maximized. Further, the fitting groove 517 and the warpage reducing groove 518 are manufactured by a simultaneous process, thereby reducing the manufacturing cost. The interval D5 between the fitting groove 517 and the warpage reducing groove 518 is 70 μm.

The method of mounting the quartz-based PLCs 501 and 502 on the quartz-based PLC503 using the spacer fiber 506 (spacer member) is the same as that of the thirteenth embodiment, and a description thereof will be omitted.

In this way, the quartz-based PLCs 501 and 502 can be mounted on the quartz-based PLC503 such that the connection end surface 51 of the quartz-based PLC501 and the connection end surface 52 of the quartz-based PLC 502 closely face each other, and a simple optical connection with sub-micron accuracy and a reduction in size of an optical circuit can be achieved.

Further, in this embodiment, since the warpage reducing grooves 508 and 518 reaching the support substrates 510 and 513 are formed in the optical waveguide layers 509 and 515 of the quartz-based PLCs 501, 502 and 503, it is possible to reduce warpage of the quartz-based PLCs 501, 502 and 503 caused by a difference in thermal expansion coefficient between the support substrates 510 and 513 made of Si and the optical waveguide layers 509 and 515 (cladding layers 511 and 514), and to suppress an increase in optical connection loss due to axial deviation and gap expansion between the quartz-based PLCs 501 and 502 caused by warpage of the quartz-based PLCs 501, 502 and 503.

Further, in this embodiment, since the fitting grooves 507 and 517 are formed to such a depth that the spacer fibers 506 are in contact with the support substrates 510 and 513, it is possible to ensure that the precision of the spacing between the quartz-based PLCs 501 and 502 and the quartz-based PLC503 is similar to that of the diameter of the spacer fibers 506.

Note that the warpage-reducing grooves 508 and 518 according to this embodiment may be filled with the filling material described in the twelfth embodiment.

[ fifteenth embodiment ]

Next, a fifteenth embodiment of the invention will be described. Fig. 22A to 22D are schematic views showing a connection structure of an optical waveguide chip according to a fifteenth embodiment of the present invention. Fig. 22A is a perspective view of a connection structure of optical waveguide chips, fig. 22B is an exploded view of parts of the connection structure, fig. 22C is a diagram showing bonding faces of three optical waveguide chips, and fig. 22D is a sectional view of the connection structure taken along the xy plane.

As shown in fig. 21A, an input optical signal 605 that has entered the quartz-based PLC 602 propagates through the optical waveguide layer of the quartz-based PLC 602, exits the quartz-based PLC 602 and enters the quartz-based PLC601, propagates through the optical waveguide layer of the quartz-based PLC601, and exits the quartz-based PLC601 as an output optical signal 604. Further, an input optical signal 620 that has entered the quartz-based PLC603 propagates through the optical waveguide layers of the quartz-based PLC603 and exits the quartz-based PLC603 as an output optical signal 619.

Like the quartz-based PLC501, the quartz-based PLC601 has a structure in which: wherein an optical waveguide layer 609 configured to transmit the input signal light 605 is formed on a supporting substrate 610 made of Si. The optical waveguide layer 609 is formed of a cladding layer 611 and a core 612, and the cladding layer 611 is formed of SiO₂As a result, the core 612 is formed in the cladding 611. Like the quartz-based PLC501, a fitting groove 607 is formed in the cladding layer 611.

In addition, in the cladding layer 611, a warpage reducing groove 608 is formed for the purpose of reducing warpage of the quartz-based PLC 601. The warpage reducing groove 608 is formed to a position reaching the supporting substrate 610 so that the supporting substrate 610 is exposed to the bottom of the warpage reducing groove 608. When the clad layer 611 is cut until the support substrate 610 is exposed, the effect of reducing the warpage of the quartz-based PLC601 can be maximized.

In this embodiment, the longitudinal direction of the fitting groove 607 and the longitudinal direction of the warpage reducing groove 608 are set to be parallel to the z-axis direction (the optical axis direction of the light exiting from the quartz-based PLC 602 to the quartz-based PLC601 and the optical axis direction of the light entering the quartz-based PLC601 or the left-right direction of fig. 22A to 22C). The quartz-based PLC601 is designed with a higher priority in consideration of reduction of transmission loss of an optical signal than warpage mitigation. That is, the two warpage reducing grooves 608 are arranged so as not to intersect the core portion 612 of the optical waveguide layer 609 and so as not to obstruct light transmission in the optical waveguide layer 609. The structure of the quartz-based PLC 602 is the same as that of the quartz-based PLC 601.

The quartz-based PLC603 has such a structure: wherein an optical waveguide layer 615 configured to transmit an input signal light 620 is formed on a supporting substrate 613 made of Si. In the optical waveguide layer 615An AWG (arrayed waveguide grating) 616. AWG616 is formed by SiO₂The input waveguide 621, input side plate waveguide 622, arrayed channel waveguide 623, output side plate waveguide 624, and output waveguide 625 in the fabricated cladding layer 614 are formed.

Further, in the cladding 614, a fitting groove 617 having the same shape as the fitting groove 607 is formed at a position of the fitting groove 607 facing the quartz-based PLCs 601 and 602 when the quartz-based PLCs 601 and 602 are mounted on the quartz-based PLC 603. In addition, in the cladding layer 614, a warpage reducing groove 618 is formed for the purpose of reducing warpage of the quartz-based PLC 603.

The warpage reducing groove 618 is formed to a position reaching the support substrate 613 so that the support substrate 613 is exposed to the bottom of the warpage reducing groove 618. When the clad layer 614 is cut until the support substrate 613 is exposed, the effect of reducing the warpage of the quartz-based PLC603 can be maximized.

As shown in fig. 22C, the shape of the warp reducing groove 618 includes not only a portion extending in the z-axis direction (the optical axis direction of light exiting from the quartz-based PLC 602 to the quartz-based PLC601 and the optical axis direction of light entering the quartz-based PLC601 or the left-right direction of fig. 22A to 22C), but also a portion extending in the x-axis direction (the direction perpendicular to the optical axis direction in the substrate plane), and the portion extending in the x-axis direction divides the arrayed channel waveguide 623 of the AWG616, the light beam that has exited from the side of the arrayed channel waveguide 623 divided by the warp reducing groove 618 enters the arrayed channel waveguide 623 on the other side across the warp reducing groove 618.

Further, in this embodiment, the warp-mitigating grooves 618 are filled with a filler material 626, wherein the thermal expansion coefficient of the filler material 626 and the constituent Substance (SiO) of the cladding layer 614₂) Are different. As the filler 626, a constituent material (SiO) having a lower hardness than the coating layer 614 is used₂) The hardness of (3). An example of such a substance is silicone. When the temperature dependence of silicone is used, the temperature dependence of AWG616 can be eliminated. Thus, the warp mitigation groove 618 filled with the filler material 626 provides both the function of mitigating warp of the quartz-based PLC603 and insulating the AWG 616.

The method of mounting the quartz-based PLCs 601 and 602 on the quartz-based PLC603 using the spacer fiber 606 (spacer member) is the same as that of the thirteenth embodiment, and a description thereof will be omitted.

In this way, the quartz-based PLCs 601 and 602 can be mounted on the quartz-based PLC603 so that the connection end surface 61 of the quartz-based PLC601 and the connection end surface 62 of the quartz-based PLC 602 closely face each other, and a simple optical connection with sub-micron accuracy and a reduction in size of an optical circuit can be achieved.

Further, in this embodiment, since the warpage reducing grooves 608 and 618 reaching the support substrates 610 and 613 are formed in the optical waveguide layers 609 and 615 of the quartz-based PLCs 601, 602 and 603, it is possible to reduce warpage of the quartz-based PLCs 601, 602 and 603 caused by a difference in thermal expansion coefficient between the support substrates 610 and 613 made of Si and the optical waveguide layers 609 and 615 (cladding layers 611 and 614), and to suppress an increase in optical connection loss due to axial deviation and gap expansion between the quartz-based PLCs 601 and 602 caused by warpage of the quartz-based PLCs 601, 602 and 603. Further, in this embodiment, the warp mitigation groove 618 is filled with a filler material 626, thereby simultaneously achieving warp mitigation for the quartz-based PLC603 and thermal isolation of the AWG 616.

Note that, in the present invention, there is no particular limitation as to in which form the input signal light is input to the PPCP or in which form the output signal light is output. That is, for the input signal light, any input method may be used, such as input through a space optical system, input through an optical fiber bonded via an optical fiber block, or input from a light emitting element/modulating element (e.g., a laser diode) that does not include an optical signal input surface on the end face of the PLC and is arranged on or inside the PLC. For the output signal light, any output method may be used, such as output by a spatial optical system, output by an optical fiber bonded via an optical fiber block, or output to a light receiving element (e.g., a photodiode) that does not include a light signal output face on the end face of the PLC and is arranged on or inside the PLC.

The optical circuits shown in each of the tenth to fifteenth embodiments include only a simple linear optical waveguide or awg, which is merely an example, and possible examples are not limited to two circuits.

In the tenth to fifteenth embodiments, spacer fibers are used as all members for joining the PLC or the substrate. As the spacer member, a member other than the spacer optical fiber or a material or a shape may be used as long as it can be appropriately fitted in the groove. More specifically, as the material of the spacer member, other than glass, metal, ceramic, polymer, or the like may be arbitrarily employed. Further, as the shape of the spacer member, a spherical shape, a trapezoidal shape, a polygonal columnar shape, an elliptical shape, or the like may be arbitrarily adopted in addition to the cylindrical shape.

In the tenth to fifteenth embodiments, each PLC (or each base) has two or more fitting grooves 107, 115, 207, 215, 307, 315, 407, 417, 507, 517, 607, or 617. The spacing fibers 106, 206, 306, 406, 506, or 606 need only be provided in a number according to the mounting grooves 107, 115, 207, 215, 307, 315, 407, 417, 507, 517, 607, or 617.

Each PLC (or each substrate) has at least warpage mitigation slots 108, 208, 308, 316, 408, 418, 508, 518, 608, or 618.

Further, in the tenth to fifteenth embodiments, the height of the spacer fiber 106, 206, 306, 406, 506, or 606 is preferably higher than the sum of the depths of the upper and lower fitting grooves in which the spacer fiber 106, 206, 306, 406, 506, or 606 is fitted.

[ sixteenth embodiment ]

In PPCP, spacer fibers and mounting grooves in the substrate and spacer fibers and mounting grooves in the quartz-based PLC require tangential contact. Typically, when a quartz-based PLC is mounted on a substrate, a self-assembly is established between the assembly grooves and the spacer fibers. However, due to internal factors such as warpage of the quartz-based PLC and the substrate or external factors such as dust or vibration, perfect assembly as shown in fig. 35D cannot always be achieved, and an error is generated in mounting accuracy.

If the warpage of the optical waveguide chip is large, sufficient tangential contact cannot be achieved on the side of the groove only by mounting the optical waveguide chip on the base such that the spacer is fitted in the two grooves of the optical waveguide chip.

Further, in order to make the optical waveguide chip have a structure detachable from the substrate using the PPCP technique, the substrate and the optical waveguide chip cannot be fixed by an adhesive or the like. Thus, if vibration, impact, heat, or the like is applied from the outside, the tangential contact between the groove and the spacer is disturbed, and an error occurs in the mounting accuracy, as described above.

The sixteenth to nineteenth embodiments of the present invention aim to stably achieve high mounting accuracy even when an optical waveguide chip is mounted by passive alignment mounting using the PPCP technique, there is warpage, dust, or vibration impact of the chip after mounting.

FIG. 23 is a perspective view showing a connection structure of an optical waveguide chip according to a sixteenth embodiment of the present invention also in this embodiment, the structures of the quartz-based PLCs 4001 and 4002 as two optical waveguide chips and the quartz-based substrate 4003 on which the quartz-based PLCs 4001 and 4002 are mounted are the same as those in the th embodiment.

Note that various functional circuits configured to process signals, such as switches and wavelength multiplexers/demultiplexers, are mounted on the optical waveguide chip as necessary. However, the present invention does not depend on the circuit arrangement in the optical waveguide chip and the function of the circuit. In practice, an appropriate optical circuit is formed in the optical waveguide chip in an arrangement avoiding a fitting groove to be described later. However, as described above, since the present invention does not depend on the arrangement of the circuit, fig. 23 shows an example including only the linear waveguide, and other circuit arrangements are omitted for the sake of simple description.

In this embodiment, a total of nine members, that is, the quartz-based PLCs 4001 and 4002 as two optical waveguide chips, the quartz-based substrate 4003 which is manufactured by the same method as the quartz-based PLCs 4001 and 4002 and does not include a waveguide, four spacer fibers (spacer members) 4006, and the pressure mechanisms 4020 which press the quartz-based PLCs 4001 and 4002, respectively, are combined, thereby forming a connection structure of the optical waveguide chips.

The quartz-based PLC4001 has a structure in which an optical waveguide layer 4008 is formed on a Si substrate 4009 as in the -embodiment, the optical waveguide layer 4008 is formed of a cladding layer 4010 and a core (not shown), the cladding layer 4010 is made of quartz glass, and the core is formed in the cladding layer 4010. furthermore, fitting grooves 4007 (second grooves) are formed in the cladding layer 4010. the structure of the quartz-based PLC4002 is the same as that of the quartz-based PLC 4001. in this embodiment, two fitting grooves 4007 are formed in PLCs.

As in the th embodiment, a quartz glass layer 4013 made of the same material as the cladding layer 4010 of the quartz-based PLCs 4001 and 4002 is formed on the surface of the Si substrate 4012 of the quartz-based substrate 4003 on which the quartz-based PLCs 4001 and 4002 are mounted.in the quartz glass layer 4013, a fitting groove 4014( th groove) is formed at a position facing the fitting groove 4007 of the quartz-based PLCs 4001 and 4002 when the quartz-based PLCs 4001 and 4002 are mounted on the quartz-based substrate 4003. as described above, since two fitting grooves 4007 are formed in PLCs, a total of four fitting grooves 4014 are formed in the quartz glass layer 4013, that is, two fitting grooves 4014 formed at a position facing the fitting groove 4007 of the quartz-based PLC4001 and two fitting grooves 4014 formed at a position facing the fitting groove 4007 of the quartz-based PLC 4002.

To manufacture the connection structure according to this embodiment, the spacer fibers 4006 are fitted in four fitting grooves 4014, respectively, formed in the silica glass layer 4013 of the silica-based substrate 4003. Then, the two spacer fibers 4006 fitted in the fitting grooves 4014 of the silica glass layer 4013 are fitted in the two fitting grooves 4007 formed in the optical waveguide layer 4008 of the silica-based PLC4001 so that the bonding surface of the silica glass layer 4013 and the bonding surface of the optical waveguide layer 4008 (cladding layer 4010) of the silica-based PLC4001 face each other, that is, so that the Si substrate 4009 is located on the upper side and the optical waveguide layer 4008 is located on the lower side, whereby the silica-based PLC4001 is mounted on the silica-based substrate 4003.

Similarly, two spacer fibers 4006 fitted in the fitting grooves 4014 of the silica glass layer 4013 are fitted in two fitting grooves 4007 formed in the optical waveguide layer 4008 of the silica-based PLC4002 so that the bonding surface of the silica glass layer 4013 and the bonding surface of the optical waveguide layer 4008 (cladding layer 4010) of the silica-based PLC4002 face each other, thereby mounting the silica-based PLC4002 on the silica-based substrate 4003.

In this way, as in the embodiment, the quartz-based PLCs 4001 and 4002 can be mounted on the quartz-based substrate 4003 by passive alignment mounting, and optical connection between the quartz-based PLC4001 and the quartz-based PLC4002 can be achieved.

The fitting grooves 4007 and 4014 are formed by photolithography and etching so that a direction in which a gap between the connection end face (entrance/exit end face) 4015 of the quartz-based PLC4001 and the connection end face (entrance/exit end face) 4016 of the quartz-based PLC4002 becomes small (an optical axis direction of light emitted from the quartz-based PLC4002 to the quartz-based PLC 4001) becomes a longitudinal direction.

The fitting groove 4007 of the quartz-based PLCs 4001 and 4002 is formed to a position reaching the Si substrate 4009 so that the Si substrate 4009 is exposed to the bottom of the fitting groove 4007 similarly, the fitting groove 4014 of the quartz-based substrate 4003 is formed to a position reaching the Si substrate 4012 so that the Si substrate 4012 is exposed to the bottom of the fitting groove 4014 as in the embodiment, this reduces the influence of an error in the height direction of the optical waveguide layer 4008 of the quartz-based PLCs 4001 and 4002 on the quartz-based substrate 4003.

The four spacer fibers 4006 each form a columnar spacer member having a diameter of, for example, 125 μm.

As a characteristic feature of this embodiment, the pressure mechanism 4020 is installed at the center of gravity position of every of the quartz-based PLCs 4001 and 4002 to press the center of gravity position the pressure mechanism 4020 presses the quartz-based PLCs 4001 and 4002 in the direction of the quartz-based substrate 4003 by its own weight.

Fig. 24A is a sectional view showing a connection structure of an optical waveguide chip before a pressure mechanism 4020 is provided. Fig. 24B is a sectional view showing the connection structure of the optical waveguide chip after the pressure mechanism 4020 is provided.

As in the th embodiment, in an optical waveguide chip such as quartz-based PLCs 4001 and 4002, an optical waveguide layer 4008 is formed on a Si substrate 4009 the Si substrate 4009, a cladding layer 4010, a core 4011, and the like are made of different materials to different thicknesses, whereby unique warpage occurs in the optical waveguide chip, the direction of warpage of the optical waveguide chip varies depending on the materials and types of the optical waveguide and the substrate, and FIG. 24A shows an example in which the warpage of the optical waveguide layer 4008 is convex with respect to the Si substrate 4009.

In the presence of such warpage, for example, as shown in FIG. 24A, microscopically, the bottom surfaces of the fitting grooves 4007 and 4014 of the quartz-based PLC4001 and the quartz-based substrate 4003 are not parallel and a tilt is generated between the bottom surfaces, even if the quartz-based PLC4001 is mounted on the quartz-based substrate 4003 by fitting the spacer fibers 4006 in the fitting groove 4014 on the quartz-based substrate 4003 side and the spacer fibers 4006 in the fitting groove 4007 on the quartz-based PLC4001 side as in the embodiment, a tangential contact between the bottom surfaces of the fitting grooves 4007 and the spacer fibers 4006 cannot be achieved due to the above-described tilt between the bottom surfaces.

If the materials, dimensions, and waveguide structures are identical in the quartz-based PLCs 4001 and 4002, the amount of increase in height is the same in the two quartz-based PLCs 4001 and 4002. That is, the floating of the two quartz-based PLCs 4001 and 4002 is the same, the relative positional deviation between the connected core positions cancels each other, and the two quartz-based PLCs 4001 and 4002 can be optically connected without positional deviation.

However, the case where the material, size, and waveguide structure are the same in the two optical waveguide chips is a very limited case. In practice, it is common to connect optical waveguide chips of different sizes made of different materials. For example, even in an optical waveguide chip like a quartz-based one, if the refractive index difference between the core material and the clad material changes, of course, the warpage or the like also changes. In this case, the above floating amount of the optical waveguide chip changes, and the position of the core in the optical waveguide is shifted between the two optical waveguide chips. In particular, in the case of arrayed waveguides or the like, loss in each waveguide channel increases, resulting in a problem in mounting.

Here, when the pressure mechanism 4020 according to this embodiment is used, the following remarkable effects can be obtained. Fig. 24B shows the positional relationship between the fitting grooves 4007 and 4014 and the spacer fiber 4006 after the pressure mechanism 4020 is mounted on the quartz-based PLC 4001. As is apparent from fig. 24B, the pressure mechanism 4020 installed at the position of the center of gravity of the quartz-based PLC4001 presses the quartz-based PLC4001 by an appropriate load in the direction of the quartz-based substrate 4003, and the warpage of the quartz-based PLC4001 is eliminated.

As a result, in this embodiment, the quartz-based PLC4001 can be prevented from floating relative to the quartz-based substrate 4003. Also for the quartz-based PLC4002, a pressure mechanism 4020 may be used to prevent floating. Therefore, in this embodiment, a great effect of eliminating the shift of the core position between the quartz-based PLC4001 and the quartz-based PLC4002 and realizing low loss connection is achieved.

Further, when the gap between the connection end faces 4015 and 4016 of the quartz-based PLCs 4001 and 4002 is filled with an index matching resin or the like, fresnel reflection of light caused by air existing in the gap between the quartz-based PLCs 4001 and 4002 can be suppressed, and a connection loss between the quartz-based PLCs 4001 and 4002 can be made small.

Fig. 25A and 25B are sectional views for explaining effects other than warp elimination according to this embodiment, and are diagrams for explaining effects of eliminating contact failure between fitting groove 4007 or 4014 and spacing optical fiber 4006 in the case where dust adheres to fitting groove 4007 or 4014 or spacing optical fiber 4006.

In the example shown in fig. 25A, small dust 4021 adheres to spacer fiber 4006 fitted in fitting groove 4007 of quartz-based PLC 4001. If the quartz-based PLC4001 is mounted on the quartz-based substrate 4003 in this state, the dust 4021 enters between the spacer fiber 4006 and the fitting groove 4007, and the quartz-based PLC4001 floats with respect to the quartz-based substrate 4003.

To solve this problem, in this embodiment, as shown in fig. 25B, when the pressure mechanism 4020 presses the quartz-based PLC4001 in the direction of the quartz-based substrate 4003, the dust 4021 on the spacer fiber 4006 moves. Therefore, an effect of achieving tangential contact between the spacer fiber 4006 and the fitting groove 4007 and achieving low-loss connection can be obtained.

In manufacturing the connection structure, the following process is preferably added: while the quartz-based PLCs 4001 and 4002 are pressed by the pressure mechanism 4020, vibration is appropriately applied to swing the quartz-based PLCs 4001 and 4002 in the horizontal direction because the dust 4021 can easily move. Note that this embodiment is effective not only in the case where dust 4021 adheres to spacing optical fiber 4006 but also in the case where dust 4021 adheres to fitting groove 4007 or 4014.

Further, in this embodiment, since the pressure mechanism 4020 is provided, the following effects can also be obtained: resonance or detachment of the connection portion, which occurs when vibration or impact is applied to the quartz-based PLCs 4001 and 4002, is prevented, and a stable connection structure is maintained.

The pressure mechanism 4020 is preferably a pressure mechanism that can apply an appropriate load to the quartz-based PLC4001 or 4002 that can eliminate the above-described contact failure between the fitting groove 4007 or 4014 and the spacer fiber 4006. in the example shown in FIG. 23, a mechanism that presses the quartz-based PLC4001 or 4002 by the weight of the pressure mechanism 4020 itself is used. as described with reference to FIG. 24B, another types of pressure mechanisms may be used as long as they can prevent floating of the quartz-based PLC4001 or 4002 with respect to the quartz-based substrate 4003.

For example, in the example shown in fig. 26A, a pressure mechanism 4020a is formed by a fixing member 4022 that holds the pressure mechanism 4020a, a bolt 4023 that is threadedly engaged with a threaded hole of the fixing member 4022, and a pressing member 4024 attached to a distal end of the bolt 4023. In the example shown in fig. 26A, when the bolt 4023 threadedly engaged with the fixing member 4022 is rotated with respect to the fixing member 4022 to which the x, y, and z-directional positions thereof are fixed, the pressing member 4024 presses the quartz-based PLC 4001.

Further, in the example shown in fig. 26B, the pressure mechanism 4020B is formed of a fixing member 4022, a bolt 4023, a pressing member 4024, and a spring mechanism 4025 (such as a coil spring or a plunger) provided between the bolt 4023 and the pressing member 4024. In the example shown in fig. 26B, the pressing member 4024 is pressed by the restoring force of the spring mechanism 4025, instead of directly pressing the pressing member 4024 by the bolt 4023, so that the quartz-based PLC4001 is pressed.

Further, the pressure mechanism may have a structure for applying pressure to the entire structure by elastic resin or the like.

Further, each of the pressure mechanisms 4020, 4020a, and 4020b is preferably integrated with a mechanism that roughly aligns the quartz base substrate 4003 with the quartz base PLCs 4001 and 4002. in order to achieve precise alignment by assembling using the PPCP technique, three steps are required, that is, a step is required to fix the quartz base substrate 4003 and roughly align the position of the quartz base substrate 4003 with all the quartz base PLCs 4001 and 4002 so that the spacer fiber 4006 is almost fitted in the fitting grooves 4007 and 4014, a step to perform precise alignment by passive alignment mounting in which the spacer fiber 4006 is fitted in the fitting grooves 4007 and 4014, and a third step to prevent floating at the time of assembly and the like by the pressure mechanisms 4020, 4020a, 4020b, or 4020 b.

Therefore, it is preferable to integrate a holding mechanism that holds the quartz-based substrate 4003, an alignment mechanism that is integrated with the holding mechanism and configured to align the mounting positions of the quartz-based PLCs 4001 and 4002, and the pressure mechanism 4020, 4020a, or 4020 b. By this integration, a more efficient installation can be achieved.

These mechanisms may be implemented by mechanical clamp structures. For example, the holding mechanism may be realized as a mechanism configured to hold the quartz-based substrate 4003 by means such as a bolt, a suction member, or a holder. Similarly, the alignment mechanism can be implemented as a mechanism configured to hold and align the quartz-based PLCs 4001 and 4002.

When the pressure mechanism 4020 is employed, the pressure mechanism 4020 is suspended from the holding mechanism and the alignment mechanism by a wire or the like, and the quartz-based PLC4001 is pressed by the weight of the pressure mechanism 4020 itself. Further, when the pressure mechanism 4020a or 4020b is employed, the fixing member 4022 is attached to the holding mechanism and the alignment mechanism.

Note that in this embodiment, an example has been described in which the quartz glass layer 4013 of the quartz base substrate 4003 is manufactured by the same process as that of the optical waveguide layer 4008 of the quartz-based PLCs 4001 and 4002, however, the quartz glass layer 4013 may be manufactured by other manufacturing methods, for example, even the same effect as described above can be obtained by V-groove processing or processing using cutting or the like or laser processing as long as the fitting grooves 4007 and 4014 by can be formed.

Further, in this embodiment, an example of connecting two optical waveguide chips has been described. However, the present invention can also be applied to connection of a plurality of (for example, three or four or more) optical waveguides.

[ seventeenth embodiment ]

Next, a seventeenth embodiment of the invention will be described. Fig. 27 is a perspective view showing a connection structure of an optical waveguide chip according to a seventeenth embodiment of the present invention, and in fig. 27, the same reference numerals as in fig. 23 denote the same components. As an example, a form similar to the connection structure of the optical waveguide chip according to the sixteenth embodiment will be described with reference to fig. 27. The pressing position of the pressure mechanism 4020c is not the position of the center of gravity of the quartz-based PLCs 4001 and 4002, but is moved to a position near the connection end faces 4015 and 4016 of the quartz-based PLCs 4001 and 4002.

Further, in the sixteenth embodiment, an example of warping has been described in which the optical waveguide layer 4008 of the quartz-based PLC4001 or 4002 becomes convex with respect to the Si substrate 4009. In this embodiment, a case where optical waveguide layer 4008 becomes concave with respect to Si substrate 4009 is assumed.

As in this embodiment, when the positions near the connection end faces 4015 and 4016 of the quartz-based PLCs 4001 and 4002 are pressed, the following effects can be obtained. That is, in this embodiment, the two quartz-based PLCs 4001 and 4002 are connected using PPCP technology, as in the sixteenth embodiment. In the quartz-based PLCs 4001 and 4002 themselves, slight warping occurs, so that the optical waveguide layer 4008 becomes concave with respect to the Si substrate 4009. The warpage occurs not only in the chip width direction (x direction) in fig. 27 but also similarly in the chip longitudinal direction (z direction).

In the sixteenth embodiment, the warpage of the quartz-based PLCs 4001 and 4002 in two axes (i.e., in the x-direction and the z-direction) can be alleviated by arranging two columnar spacer fibers 4006 having a longitudinal direction of the z-direction for each chip in the x-axis direction and pressing the gravity center position of each of the quartz-based PLCs 4001 and 4002 to the quartz-based substrate 4003 side.

On the other hand, in , in this embodiment, since the direction of warpage in the quartz-based PLCs 4001 and 4002 is opposite to that in the sixteenth embodiment, the pressure mechanism configured to press the quartz-based PLCs 4001 and 4002 toward the quartz-based substrate 4003 side is pressed toward the center of gravity position of the quartz-based PLCs 4001 and 4002, so that pressing is performed in a direction to increase the warpage.

To prevent this, in this embodiment, the position to be pressed by the pressure mechanism 4020c is moved from the position of the center of gravity of the quartz-based PLCs 4001 and 4002 to a position near the connection end faces 4015 and 4016.

Fig. 28A is a sectional view showing a connection structure of an optical waveguide chip before a pressure mechanism 4020c is provided. Fig. 28B is a sectional view showing the connection structure of the optical waveguide chip after the pressure mechanism 4020c is provided.

When the positions near the connection end surfaces 4015 and 4016 of the quartz-based PLCs 4001 and 4002 are pressed, as shown in fig. 28B, the quartz-based PLCs 4001 and 4002 are inclined, the fitting grooves 4007 and 4014 can be brought into tangential contact with the spacer fiber 4006 near the connection end surfaces 4015 and 4016, and a state in which the quartz-based PLCs 4001 and 4002 float with respect to the quartz-based substrate 4003 near the connection end surfaces 4015 and 4016 can be eliminated.

Here, the portion actually required to be aligned for the purpose of the present invention is a portion in the vicinity of the connection end faces 4015 and 4016 of the two quartz-based PLCs 4001 and 4002. In this way, the quartz-based PLCs 4001 and 4002 are tilted by the pressing of the pressure mechanism 4020c, and the fitting between the fitting grooves 4007 and 4014 and the spacer fiber 4006 is correctly established near the connection end faces 4015 and 4016, so that the optical connection loss between the quartz-based PLCs 4001 and 4002 is greatly reduced.

Further, in this embodiment, the fitting between the fitting grooves 4007 and 4014 and the spacer fiber 4006 is properly established only in the vicinity of the connection end faces 4015 and 4016 of the quartz-based PLCs 4001 and 4002. This can achieve low connection loss even if there is warpage in the quartz-based substrate 4003.

Note that, in this embodiment, the optical axes of the optical waveguides in the two quartz-based PLCs 4001 and 4002 are slightly inclined in the thickness direction (y direction). However, when the gap between the connection end faces 4015 and 4016 of the quartz-based PLCs 4001 and 4002 is filled with an index matching resin or the like, the connection loss caused by the inclination of the optical axis becomes sufficiently small.

Further, in this embodiment, even if dust or the like exists between the fitting grooves 4007 and 4014 and the spacing fiber 4006, the dust can be moved as in the sixteenth embodiment. In addition, the assembly between assembly grooves 4007 and 4014 and spacer fiber 4006 is important only in the vicinity of connection end faces 4015 and 4016. Thus, even if dust exists in portions other than the vicinity of the connection end surfaces 4015 and 4016, there is no problem in assembly in the vicinity of the connection end surfaces 4015 and 4016, and the dust-proof capability can be improved.

Further, in this embodiment, since the pressure mechanism 4020c is provided, the following effects can also be obtained: resonance or detachment of the connection portion, which occurs when vibration or impact is applied to the quartz-based PLCs 4001 and 4002, is prevented, and a stable connection structure is maintained.

As the pressure mechanism 4020c, a form of a pressure mechanism 4020 using weight may be employed as in the sixteenth embodiment, or a form of a pressure mechanism 4020a or 4020B described with reference to fig. 26A or 26B may be employed.

However, as shown in the perspective view of FIG. 29A and the cross-sectional view of FIG. 29B, even when the common pressure mechanism 4020d is disposed in the vicinity of the connection end faces 4015 and 4016 of the quartz-based PLCs 4001 and 4002, the same effects as described above can be obtained.

When three optical waveguide chips are connected by the PPCP, for example, when another quartz-based PLC is disposed next to steps on the right side of the quartz-based PLC4002 in FIGS. 27 to 29 and optical connection is made, a pressure mechanism configured to press a position near the connection end face of the quartz-based PLC and the quartz-based PLC4002 is provided as described above.

[ eighteenth embodiment ]

Next, an eighteenth embodiment of the invention will be described. Fig. 30 is a perspective view showing a connection structure of an optical waveguide chip according to an eighteenth embodiment of the present invention, and in fig. 30, the same reference numerals as in fig. 23 denote the same components. As an example, a form similar to the connection structure of the optical waveguide chip according to the sixteenth embodiment will be described with reference to fig. 30. The pressing position of the pressure mechanism 4020e is not the center of gravity position of the quartz-based PLCs 4001 and 4002. The pressure mechanism 4020e is installed at a position directly above the spacer fiber 4006 fitted in the fitting grooves 4007 of the quartz-based PLCs 4001 and 4002.

In the example shown in fig. 30, two fitting grooves 4007 and two fitting grooves 4014 extending in the chip longitudinal direction (z direction) are formed for each chip pressure mechanisms 4020e are mounted on each fitting groove a total of two pressure mechanisms 4020e are mounted in each chip note that when fitting grooves extending in the chip width direction (x direction) are provided, the pressure mechanisms 4020e are mounted immediately above them along the interval optical fibers fitted in the grooves.

Fig. 31 is a sectional view showing the connection structure of the optical waveguide chip after the pressure mechanism 4020e is provided. In this example, a position directly above spacer fiber 4006 (fitting grooves 4007 and 4014) is pressed, thereby obtaining the following effects. That is, in this embodiment, in both the case where the optical waveguide layer 4008 has a warp that is convex with respect to the Si substrate 4009 and the case where the optical waveguide layer 4008 has a warp that is concave, tangential contact between the fitting grooves 4007 and 4014 and the spacing optical fiber 4006 can be achieved by pressing by the pressing mechanism 4020e as shown in fig. 24B, and a state where the quartz-based PLCs 4001 and 4002 float with respect to the quartz-based substrate 4003 can be solved. Therefore, in this embodiment, a great effect of eliminating the shift of the core position between the quartz-based PLCs 4001 and 4002 and realizing low loss connection is achieved.

In the sixteenth and seventeenth embodiments, a position not directly above the spacer fiber 4006 (fitting grooves 4007 and 4014) is pressed. In this way, excessive pressing causes reverse warpage of the quartz-based PLCs 4001 and 4002 or deterioration of optical characteristics because of a phenomenon similar to the case where the center of the beam having the fixed end is pressed. Therefore, the pressing force needs to be set appropriately.

Further , in this embodiment, a load is directly applied to the spacer fiber 4006 and the fitting grooves 4007 and 4014 since the spacer fiber 4006 intervenes in a portion where the load is applied, there is no fear of the above-mentioned reverse warping of the quartz-based PLCs 4001 and 4002 and it is easy to set a pressing force, further, since it is not necessary to largely correct the warping of the quartz-based PLCs 4001 and 4002, it is possible to realize tangential contact between the fitting grooves 4007 and 4014 and the spacer fiber 4006 by a relatively small force and it is possible to prevent floating of the quartz-based PLCs 4001 and 4002.

Further, as in the sixteenth and seventeenth embodiments, if dust or the like exists between the fitting grooves 4007 and 4014 and the spacing fiber 4006, the dust can be moved. In this embodiment, since the load concentrated on fitting grooves 4007 and 4014 and spacing fiber 4006 is large, the effect of removing dust between fitting grooves 4007 and 4014 and spacing fiber 4006 is large, and the dust-proof capability can be improved.

Further, in this embodiment, since the pressure mechanism 4020e is provided, the following effects can also be obtained: resonance or detachment of the connection portion, which occurs when vibration or impact is applied to the quartz-based PLCs 4001 and 4002, is prevented, and a stable connection structure is maintained.

As the pressure mechanism 4020e, a form of a pressure mechanism 4020 using weight may be employed as in the sixteenth embodiment, or a form of a pressure mechanism 4020a or 4020B described with reference to fig. 26A or 26B may be employed.

Note that in the sixteenth to eighteenth embodiments, a Planar Lightwave Circuit (PLC) of a thin glass film formed on a silicon substrate has been described as an optical waveguide chip by way of example. However, the present invention can be applied to any optical waveguide chip including a waveguide mechanism. For example, as a material of the substrate or the optical waveguide, quartz, a polymer made of an organic substance, a semiconductor or compound semiconductor waveguide using Si, silicon nitride (SiN), gallium arsenide, indium phosphide (InP), or the like, and a dielectric such as Lithium Niobate (LN), Periodically Polarized Lithium Niobate (PPLN), or Lithium Tantalate (LT) can be used in addition to quartz glass. These materials can be similarly applied to the following nineteenth embodiment.

[ nineteenth embodiment ]

Next, a nineteenth embodiment of the present invention will be described fig. 32 is a side view showing a connection structure of an optical waveguide chip according to the nineteenth embodiment of the present invention, fig. 33A is a plan view of a pressure mechanism according to the embodiment viewed from an upper side, fig. 33B is a diagram showing a bonding surface of the optical waveguide chip to a substrate, and fig. 34 is a sectional view showing the connection structure of the optical waveguide chip, this embodiment shows an example of a mounting form of a PPCP using a light emitting element and a waveguide as another example of the present invention.

In this embodiment, an optical waveguide chip (laser waveguide chip) 4002f and an optical waveguide chip 4001g which transmits light from the optical waveguide chip 4002f to the optical fiber 4028 are mounted on a quartz-based substrate 4003 f. As the optical waveguide chip 4002f, a DFB (distributed feedback) laser chip made of a III-V group material such as InP is used. In addition to the DFB laser, a DBR (distributed bragg reflector) laser, an SOA (semiconductor optical amplifier), or the like can be used. Electrical wires and connection pads electrically connected to a driver configured to drive the DFB laser are not shown in the figure.

Here, the optical waveguide chip 4002f includes a Si substrate 4009f, the above-described DFB laser 4030 formed on the Si substrate 4009f, and an optical waveguide layer 4008 f. The structure in which fitting groove 4007f is formed in the cladding layer of optical waveguide layer 4008f is the same as that in the sixteenth embodiment. A core 4011f configured to guide a light beam from the DFB laser 4030 is formed in the optical waveguide layer 4008 f. Further, a spot-size converter 4031 for bringing the diameter of the light beam from the DFB laser 4030 close to the diameter of the core portion 4011g in the optical waveguide layer 4008g of the optical waveguide chip 4001g is integrated in the vicinity of the connection end face with the optical waveguide chip 4001g of the optical waveguide layer 4008 f.

The optical waveguide chip 4002f is mounted such that output light is connected to the core 4011g in the connection end face of the optical waveguide chip 4001g by the PPCP technique of the present invention.

The optical waveguide chip 4001g includes a Si substrate 4009g and an optical waveguide layer 4008g formed on the Si substrate 4009 g. the structure in which fitting grooves 4007g are formed in the cladding layer of the optical waveguide layer 4008g is the same as that in the sixteenth embodiment furthermore, fitting grooves 4007h are added to the cladding layer of the optical waveguide layer 4008g, the longitudinal direction of the fitting grooves 4007h being perpendicular to the optical axis direction (z direction) of light entering from the optical waveguide chip 4002f to the optical waveguide chip 4001g in the joint plane.

Light propagating through the optical waveguide layer 4008g of the optical waveguide chip 4001g is output from the connection end face on the opposite side of the optical waveguide chip 4002f to each of the optical fibers 4028 via a lens (not shown), or is directly output to each of the optical fibers 4028.

The substrate 4003f according to this embodiment is made of Si, ceramic such as LTCC (low temperature co-fired ceramic), aluminum nitride, or the like in of the manufacturing process and the post-process (etching or processing) of the substrate 4003f, mounting grooves 4014f to be mounted on the spacer fibers 4006f and 4006g are formed, and further, mounting grooves 4014h are formed in the substrate 4003f at positions facing the mounting grooves 4007h of the optical waveguide chip 4001 g.

When manufacturing the connection structure of the optical waveguide chips 4001g and 4002f, the spacer fiber 4006f is fitted in the fitting groove 4014f on the substrate 4003f side. Then, the spacer optical fiber 4006f fitted in the fitting groove 4014f is fitted in the fitting groove 4007f on the optical waveguide chip 4002f side so that the bonding surface of the substrate 4003f and the bonding surface of the optical waveguide chip 4002f face each other, thereby mounting the optical waveguide chip 4002f on the substrate 4003 f.

Similarly, spacer optical fibers 4006g are fitted in fitting grooves 4014f on the substrate 4003f side, and spacer optical fibers 4006h are fitted in fitting grooves 4014h the spacer optical fibers 4006g fitted in the fitting grooves 4014f are fitted in the fitting grooves 4007g on the optical waveguide chip 4001g side so that the bonding surface of the substrate 4003f and the bonding surface of the optical waveguide chip 4001g face each other, and the spacer optical fibers 4006h fitted in the fitting grooves 4014h are fitted in the fitting grooves 4007h on the optical waveguide chip 4001g side, whereby the optical waveguide chip 4001g is mounted on the substrate 4003 f.

In this embodiment, the pressure mechanisms 4020f and 4020g are mounted on the optical waveguide chips 4002f and 4001g, respectively.

The pressure mechanism 4020f is formed of an -th pressing member 4026f and a second pressing member 4027f, and the -th pressing member 4026f is made of an elastic resin and mounted on the optical waveguide chip 4002f such that a pressing position is provided directly above the spacer fiber 4006f fitted in the fitting groove 4007f, and the second pressing member 4027f is mounted on the -th pressing member 4026f and is configured to press the -th pressing member 4026 f.

The pressure mechanism 4020g is formed of -th pressing members 4026g and 4026h and a second pressing member 4027g, -th pressing members 4026g and 4026h are made of an elastic resin and mounted on the optical waveguide chip 4001g such that pressing positions are provided directly above the spacer fibers 4006g and 4006h fitted in the fitting grooves 4007g and 4007h, and the second pressing member 4027g is mounted on the -th pressing members 4026g and 4026h and configured to press the -th pressing members 4026g and 4026 h.

In this embodiment, the pressure mechanisms 4020f and 4020g are provided, thereby obtaining the following significant effects. That is, in this embodiment, in both the case where the optical waveguide layers 4008f and 4008g have a warp that is convex with respect to the Si substrates 4009f and 4009g and the case where the optical waveguide layers 4008f and 4008g have a concave warp, tangential contact between the fitting grooves 4007f, 4007g, 4007h, 4014f, and 4014h and the spacing optical fibers 4006f, 4006g, and 4006h can be achieved by pressing by the pressing mechanisms 4020f and 4020g as shown in fig. 24B, and a state where the optical waveguide chips 4002f and 4001g float with respect to the base 4003f can be solved. Therefore, in this embodiment, a great effect of eliminating the shift of the core position between the optical waveguide chips 4002f and 4001g and realizing low loss connection is achieved.

Further, in the eighteenth embodiment, the pressure mechanisms 4020e are mounted directly at positions directly above the spacer optical fibers 4006 fitted in the fitting grooves 4007 it is necessary to make provision so that the pressing force of each of the plurality of pressure mechanisms 4020e mounted on optical waveguide chips becomes constant.

On the other hand, , as in this embodiment, when a member of elastic resin (for example, silicone rubber) is used as the th pressing members 4026f, 4026g, and 4026h, and a common second pressing member 4027f which presses the plurality of th pressing members 4026f and a common second pressing member 4027g which presses the plurality of th pressing members 4026g and 4026h are used, a pressure mechanism can be shared.

When the plurality of th pressing members 4026f made of elastic resin are respectively deformed by a load from the second pressing member 4027f in accordance with the presence/absence of dust or warpage or floating of the optical waveguide chip 4002f, as shown in fig. 34, an appropriate load is applied to each of the spaced optical fibers 4006f and floating of the optical waveguide chip 4002f can be more effectively prevented, similarly, when the plurality of th pressing members 4026g and 4026h are respectively deformed by a load from the second pressing member 4027g, an appropriate load is applied to each of the spaced optical fibers 4006g and 4006h, and floating of the optical waveguide chip 4001g can be prevented.

Further, as in the sixteenth to eighteenth embodiments, even if dust or the like exists between the fitting grooves 4007f, 4007g, 4007h, 4014f, and 4014h and the spacing fibers 4006f, 4006g, and 4006h, the dust can be moved. In this embodiment, since the load concentrated on fitting grooves 4007f, 4007g, 4007h, 4014f, and 4014h and spacing fibers 4006f, 4006g, and 4006h is large, the effect of removing dust between fitting grooves 4007f, 4007g, 4007h, 4014f, and 4014h and spacing fibers 4006f, 4006g, and 4006h is large, and the dust-proof capability can be improved.

Further, in this embodiment, since the pressure mechanisms 4020f and 4020g are provided, the following effects can also be obtained: resonance or detachment of the connection portion, which occurs when vibration or impact is applied to the optical waveguide chips 4002f and 4001g, is prevented, and a stable connection structure is maintained.

As the second pressing members 4027f and 4027g, the form of a pressure mechanism 4020 using weight may be employed as in the sixteenth embodiment, or the form of a pressure mechanism 4020a or 4020B described with reference to fig. 26A or 26B may be employed.

In the sixteenth to nineteenth embodiments, only an example of a simple waveguide connection is shown. However, any optically functional structure may be integrated. For example, a switching function, a wavelength multiplexing/demultiplexing function, a polarization integration function, a mach-zehnder interference circuit, a ring resonator, a phase adjustment circuit, and the like may be provided. Alternatively, a laser, a photodiode, or the like including a waveguide mechanism may be provided. In addition, a waveguide having a large nonlinear effect can be used.

In the sixteenth to nineteenth embodiments, regarding the fitting grooves 4007 and 4007f to 4007h, each optical waveguide chip has two or more fitting grooves. The fitting grooves 4014, 4014f, or 4014h formed in the quartz-based substrate 4003 or 4003f need only be provided in number according to the fitting grooves 4007 and 4007f to 4007 h. For spacing fibers 4006 and 4006f to 4006h, the spacing fibers need only be set in number according to fitting grooves 4007, 4007f to 4007h, 4014f, and 4014 h.

In the sixteenth to nineteenth embodiments, the height of the spacer fibers 4006 and 4006f to 4006h is preferably larger than the sum of the depth of the fitting grooves 4014, 4014f and 4014h on the base side and the depth of the fitting grooves 4007 and 4007f to 4007h on the optical waveguide chip side. This may provide a gap between the substrate and the optical waveguide chip.

In the sixteenth to nineteenth embodiments, examples have been described in which the fitting grooves 4007, 4007f to 4007h, 4014f, and 4014h are grooves each having a rectangular cross section. However, grooves whose groove widths are narrowed toward the substrates 4009, 4009f, 4009g, 4012, and 4012f, for example, grooves each having a V-shaped or W-shaped cross section or grooves each having a U-shaped cross section, may be used.

In the sixteenth to nineteenth embodiments, the planar shape of the fitting grooves 4007, 4007f to 4007h, 4014f, and 4014h as viewed from the upper side is a rectangular shape. However, the planar shape may be any shape, such as a circular, polygonal, or elliptical shape, if the same effect can be obtained. That is, the fitting grooves 4007, 4007f to 4007h, 4014f, and 4014h may vary in width in the longitudinal direction.

In addition, in the sixteenth to nineteenth embodiments, the cylindrical spacer fibers 4006 and 4006f to 4006h are used as the spacer member, however, the present invention is not limited thereto the material of the spacer member may be any material, for example, an inorganic substance such as glass, metal or polymer, furthermore, the shape is not limited as long as it can be suitably fitted in of the fitting grooves 4007, 4007f to 4007h, 4014f and 4014 h.

Further, if the height of the spacer member is changed when the spacer member is fitted in the fitting groove, the optical waveguide chip may be inclined with respect to the substrate. Therefore, the material, size, and shape of the spacer member are preferably set so that the height thereof is difficult to change when the spacer member is fitted in the fitting groove and pressed from above.

INDUSTRIAL APPLICABILITY

The present invention can be applied to a technique of connecting optical waveguide chips.

Description of reference numerals and symbols

11. 11b, 12b … connecting end faces, 13-17 … cuts, 108, 208, 308, 316, 408, 418, 508, 518, 608, 618 … warpage relieving slots, 317, 318, 626 … filler material, 2001a-2001c, 2002a-2002c, 2017-2019, 2017a-2019a, 3001a-3001d, 3002a-3002d, 3016, 3017, 101, 102, 201, 202, 301, 401-403, 501-503, 601-603, 4001, 4002 … quartz-based PLCs, 2003a-2003c, 3003c, 3003d, 103, 203, 303, 4003f … substrates, 2006a, 2016, 3006, 106, 206, 306, 406, 506, 606, 6, 4006 f-6 h, … h spacing optical fibers, 2007, 2013, 3013 a, 3013d, 2015 3, 3013c, 4007 c, 2015 3d, 4007 c, 2015 3, 207 c, 4007 c, 4001, 4003 d, 207, 115 c, and 4003 d, 307. 315, 407, 417, 507, 517, 607, 617, 4007f-4007h, 4014f, 4014h …, 2008, 2024, 3008, 109, 209, 309, 409, 415, 509, 515, 609, 615, 4008f, 4008g … optical waveguide layer, 2009, 3009, 4009f, 4009g, 4012f … silicon substrate, 2010, 111, 211, 311, 411, 414, 511, 514, 611, 614, 4010 … cladding layer, 2011, 3011, 112, 401212, 312, 402412, 416, 512, 516, 612, 4011f, 4018651 g … core, 2012, 3012, 114, 214, 314, 4013f … glass layer, optical waveguide chip, 2021 …, 2022 …, 2023 b, 2023015, 3015, 3012, 4022, 114, 214, 314, 4013f, 40224 glass layer, optical waveguide chip, 2021, 2022 364625, 2022 b, 2027 b, 3015, 3014, 2022, 4023, 4024, 736 a, 736, 734, 736 a, and spot size conversion mechanism, 4026h, 4027f, 4027g … pressing members, 4025 … spring mechanism.