阅读说明：本技术 用于半导体光波导的热光移相器 (Thermo-optic phase shifter for semiconductor optical waveguide ) 是由 西恩·P·安德森 唐纳德·亚当斯 于 2018-04-06 设计创作，主要内容包括：实施例包括用于对光信号进行移相的方法和相关联的装置。该方法包括：在光波导的第一端处接收具有第一相位的光信号,该光波导形成于半导体层中并沿第一轴延伸。该方法还包括：在光波导的与第一端相对的第二端处发送具有第二相位的经修改的光信号,其中第二相位不同于第一相位。发送经修改的光信号包括：在第一接触区域和第二接触区域之间施加电压信号,该第一接触区域和第二接触区域远离第一轴形成于半导体层中。施加电压信号导致电流沿光波导的尺寸被传导。电流导致对光波导的电阻加热以及第一相位和第二相位之间的期望相移。(Embodiments include methods and associated apparatus for phase shifting an optical signal. The method comprises the following steps: an optical signal having a first phase is received at a first end of an optical waveguide formed in a semiconductor layer and extending along a first axis. The method further comprises the following steps: transmitting the modified optical signal having a second phase at a second end of the optical waveguide opposite the first end, wherein the second phase is different from the first phase. Transmitting the modified optical signal comprises: a voltage signal is applied between a first contact region and a second contact region formed in the semiconductor layer away from the first axis. Application of a voltage signal causes current to be conducted along the dimensions of the optical waveguide. The current causes resistive heating of the optical waveguide and a desired phase shift between the first phase and the second phase.)

1. An apparatus, comprising:

an optical waveguide formed in the semiconductor layer;

a first contact region formed in the semiconductor layer and intersecting the optical waveguide; and

a first optical transition region extending between the optical waveguide and the first contact region,

wherein the first contact region is electrically coupled with the first optical transition region and is configured to conduct an electrical current along a dimension of the optical waveguide to apply resistive heating to the optical waveguide.

2. The apparatus of claim 1, wherein the optical waveguide extends along a first axis in the semiconductor layer, and

wherein the first contact region extends in the semiconductor layer along a second axis, the second axis being substantially perpendicular to the first axis.

3. The apparatus of claim 2, wherein the first optical transition region defines a linear taper between the optical waveguide and the first contact region.

4. The apparatus of claim 2, wherein the first optical transition region defines a curved taper between the optical waveguide and the first contact region.

5. The apparatus of claim 4, wherein the first optical transition region comprises a first ellipse overlapping the optical waveguide, wherein the first ellipse has a major axis aligned with the first axis and a minor axis aligned with the second axis.

6. The apparatus of claim 5, wherein a ratio of the major axis to the minor axis is about 4: 1.

7. the device of any of claims 1-6, wherein the first contact region has a first doping level that is greater than a second doping level of the optical waveguide.

8. The apparatus of claim 7, wherein the first contact region is coupled with a first metal contact.

9. The device of any one of claims 1 to 8, wherein current is conducted over the width of the optical waveguide.

10. The apparatus of any of claims 1 to 9, further comprising:

a second contact region formed in the semiconductor layer and intersecting the optical waveguide; and

a second optical transition region extending between the optical waveguide and the second contact region,

wherein applying a voltage signal between the first contact region and the second contact region causes an electrical current to be conducted along the length of the optical waveguide.

11. The apparatus of claim 10, wherein a length of the optical waveguide is selected to provide a desired resistance for the resistive heating.

12. The apparatus of any of claims 1 to 11, further comprising:

a base layer; and

a dielectric layer at least partially disposed between the semiconductor layer and the substrate,

wherein the base layer defines a removed area that overlaps at least one of: the optical waveguide, the first contact region, and the first optical transition region.

13. An apparatus, comprising:

an optical waveguide formed in the semiconductor layer and extending along a first axis, the optical waveguide having a first doping level; and

a first contact region and a second contact region formed in the semiconductor layer away from the first axis, wherein the first contact region and the second contact region each have a respective second doping level, the second doping level being greater than the first doping level,

wherein in response to a voltage signal applied between the first contact region and the second contact region, current is conducted along a dimension of the optical waveguide, and

wherein resistive heating of the optical waveguide is provided by the electrical current.

14. The apparatus of claim 13, wherein the optical waveguide defines a first optical transition region extending away from the first axis, and

wherein the first contact region is electrically coupled with the first optical transition region.

15. The apparatus of claim 14, wherein the second contact region is electrically coupled with the first optical transition region.

16. The device of any one of claims 13 to 15, wherein each of the first and second contact regions extends along a respective second axis, the second axis being substantially perpendicular to the first axis.

17. A method, comprising:

receiving an optical signal having a first phase at a first end of an optical waveguide formed in a semiconductor layer and extending along a first axis; and

transmitting a modified optical signal having a second phase at a second end of the optical waveguide opposite the first end, wherein the second phase is different from the first phase,

wherein transmitting the modified optical signal comprises:

applying a voltage signal between a first contact region and a second contact region formed in the semiconductor layer away from the first axis, wherein applying the voltage signal causes a current to be conducted along a dimension of the optical waveguide, wherein the current causes resistive heating of the optical waveguide and a desired phase shift between the first phase and the second phase.

18. The method of claim 17, wherein the optical waveguide defines a first optical transition region extending away from the first axis, and

wherein the first contact region is electrically coupled with the first optical transition region.

19. The method of claim 18, wherein the second contact region is electrically coupled with the first optical transition region.

20. The method of any of claims 17-19, wherein each of the first and second contact regions extends along a respective second axis, the second axis being substantially perpendicular to the first axis.

Technical Field

Embodiments presented in this disclosure relate generally to photonics, and more particularly, to thermo-optic phase shifters formed in the same semiconductor layer as optical waveguides.

Background

In photonic circuits, thermo-optic phase shifters are commonly used as optical biasing or tuning elements (e.g., in modulators or tunable filters). In general, to fabricate smaller and/or low power optical devices and to provide a greater tuning range within a given power budget, it may be desirable to increase the efficiency of thermo-optic phase shifters.

One technique for improving the efficiency of thermo-optic phase shifters involves placing a significant heating element in proximity to the optical waveguide, which reduces the amount of heat coupled into other nearby elements (e.g., substrates). However, the proximity of the heating elements tends to increase optical insertion loss. Another technique for improving the efficiency of thermo-optic phase shifters includes thermally isolating the heating element and/or optical waveguide from other elements (e.g., substrates) using air grooves or other insulating material(s).

Drawings

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

FIG. 1 illustrates an exemplary apparatus for conducting current along a width of an optical waveguide according to one embodiment.

FIG. 2 illustrates major and minor axes of an elliptical optical transition region according to one embodiment.

FIG. 3 illustrates an exemplary optical transition region defining a linear taper (taper) according to one embodiment.

FIG. 4 illustrates an exemplary doping profile for a thermo-optic phase shifter according to one embodiment.

FIG. 5 illustrates an exemplary apparatus for conducting current along a length of an optical waveguide according to one embodiment.

FIG. 6 illustrates a plurality of layers including thermo-optic phase shifters in semiconductor layers according to one embodiment.

FIG. 7 illustrates a plurality of layers having regions removed from a base layer, according to one embodiment.

FIG. 8 illustrates an exemplary method of phase shifting an optical signal according to one embodiment.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.

Detailed Description

SUMMARY

Aspects of the invention are set out in the independent claims, with preferred features set out in the dependent claims. Features of one aspect may be applied to each aspect individually or in combination with the other aspects.

One embodiment presented in the present disclosure is an apparatus comprising: an optical waveguide formed in the semiconductor layer; a first contact region formed in the semiconductor layer and intersecting the optical waveguide; and a first optical transition region extending between the optical waveguide and the first contact region. The first contact region is electrically coupled to the first optical transition region and is configured to conduct an electrical current along a dimension of the optical waveguide to apply resistive heating to the optical waveguide.

Another embodiment is an apparatus comprising an optical waveguide formed in a semiconductor layer and extending along a first axis, the optical waveguide having a first doping level. The device also includes a first contact region and a second contact region formed in the semiconductor layer away from the first axis, wherein the first contact region and the second contact region each have a respective second doping level that is greater than the first doping level. In response to a voltage signal applied between the first contact region and the second contact region, a current is conducted along a dimension of the optical waveguide, and resistive heating of the optical waveguide is provided by the current.

Another embodiment is a method comprising: an optical signal having a first phase is received at a first end of an optical waveguide formed in a semiconductor layer and extending along a first axis. The method further comprises the following steps: transmitting the modified optical signal having a second phase at a second end of the optical waveguide, wherein the second end is opposite the first end, the second phase being different from the first phase. Transmitting the modified optical signal comprises: a voltage signal is applied between a first contact region and a second contact region formed in the semiconductor layer away from the first axis. Applying the voltage signal causes a current to be conducted along a dimension of the optical waveguide, and the current causes resistive heating of the optical waveguide and a desired phase shift between the first phase and the second phase.

Example embodiments

Embodiments of the present disclosure generally relate to implementations of thermo-optic phase shifters formed in the same semiconductor layer as the optical waveguides. In some embodiments, at least a first contact region is formed in the semiconductor layer and is configured to conduct current along a dimension of the optical waveguide to apply resistive heating to the optical waveguide. The dimension may be a width or a length of the optical waveguide. In this way, the optical waveguide itself may be used as a resistive heating element, such that the device need not include a separate heating element.

In some embodiments, the device includes at least a first optical transition region extending between the optical waveguide and the first contact region. The first optical transition region has a shape and a size such that: the shape and size are selected to mitigate optical losses that may typically occur due to the intersection of the first contact region with the optical waveguide. In some embodiments, the first optical transition region defines a linear taper between the optical waveguide and the first contact region. In other embodiments, the first optical transition region defines a curved taper between the optical waveguide and the first contact region. For example, the first optical transition region may be an ellipse overlapping the optical waveguide, wherein a major axis of the ellipse is aligned with a longitudinal axis of the waveguide and a minor axis of the ellipse is substantially perpendicular to the longitudinal axis.

In some embodiments, the first contact region has a first doping level that is greater than a second doping level of the optical waveguide. In one embodiment, the first optical transition region also has a second doping level. In this way, the electrical resistance in the optical waveguide and/or the first optical transition region may be greater than the electrical resistance in the first contact region, so that the current tends to concentrate heat at the optical mode and to minimize heat loss to other parts of the photonic platform.

Fig. 1 illustrates an exemplary apparatus 100 for conducting current along the width of an optical waveguide according to one embodiment. In some embodiments, the apparatus 100 is formed within a single semiconductor layer, such as a silicon-on-insulator (SOI) based photonic platform that includes multiple optical components. Embodiments are also possible using suitable alternative semiconductor material(s).

The apparatus 100 includes an optical waveguide 105 extending along a first axis in a semiconductor layer. As shown, the first axis corresponds to the X axis. The device 100 also includes a contact region 110 formed in the semiconductor layer and intersecting the optical waveguide 105. In some embodiments, the contact region 110 extends along a second axis in the semiconductor layer. In some embodiments, the second axis is substantially perpendicular to the first axis. As shown, the second axis corresponds to the Y axis. However, in other embodiments, the contact region 110 may intersect the optical waveguide 105 at other suitable angles. In some embodiments, the contact regions 110 extend to both sides of the optical waveguide 105 (i.e., in the positive Y-direction and the negative Y-direction). In other embodiments, the contact region 110 extends to only one side of the optical waveguide 105. Furthermore, although the extent of the contact region 110 on the first side of the optical waveguide 105 is depicted as being substantially the same as the extent of the contact region 110 on the second side of the optical waveguide 105, this is not required.

As shown, the contact region 110 is connected to two metal contacts 120-1, 120-2, but other suitable conductive materials are possible for the contacts 120-1, 120-2. The contact 120-1 is setOn a first side of the optical waveguide 105 and the contact 120-2 is disposed on an opposite second side of the optical waveguide. The contact area 110 is connected via contacts 120-1, 120-2 to a voltage source 125, which voltage source 125 is configured to apply a voltage signal v across the optical waveguide 105. The voltage signal v causes a current 135 to pass between the contacts 120-1, 120-2 along the dimension of the optical waveguide 105. As shown, the dimension of the optical waveguide 105 is the width of the optical waveguide 105, which is substantially aligned with the Y-axis. Due to the thermoelectric nature, the current 135 causes heating of the optical waveguide 105 such that the apparatus 100 is configured to receive a signal having a first phase Φ at the optical waveguide 105 ₁And transmits an optical signal having a second phase phi (the "optical input") ₂Wherein the second phase Φ ₂Different from the first phase phi ₁。

The device 100 also includes an optical transition region 115 extending between the optical waveguide 105 and the contact region 110. The optical transition region 115 has a shape and size selected to mitigate optical losses that may typically occur due to the intersection of the contact region 110 with the optical waveguide 105. For example, the dimensions of the optical transition region 115 may be selected based on one or more of the wavelength of the received first optical signal and the dimensions of the optical waveguide 105 (e.g., the width of the optical waveguide 105 in the Y-direction, the thickness of the semiconductor layer in the Z-direction). One or more tapered regions 130 are defined by the optical transition region 115 and extend between the optical waveguide 105 and the contact region 110.

In other embodiments, the optical transition region 115 (more specifically, the tapered region 130) defines a curved taper between the optical waveguide 105 and the contact region 110. For example, as shown in fig. 1 and 2, the optical transition region 115 may be an ellipse 200 that overlaps the optical waveguide 105. Other shapes of the optical transition region 115 with a curved taper (e.g., circular, semi-elliptical, etc.) are also possible. In some cases, the ellipse 200 is centered at the intersection (interaction) of the optical waveguide 105 and the contact region 110. In some embodiments, the major axis 205 of the ellipse 200 is aligned with the major axis of the optical waveguide 105 (as shown, along the X-axis), and the minor axis 210 of the ellipse 200 is aligned with the major axis of the contact region 110 (as shown, along the Y-axis and substantially perpendicular to the major axis of the optical waveguide 105). In one embodiment, the ratio of the major axis 205 to the minor axis 210 is about 4: 1. For example, for a 10 micrometer (μm) major axis 205, the minor axis 210 is about 2.5 μm. This ratio corresponds to the lowest optical loss of the device 100.

In some embodiments, the optical transition region 115 (more specifically, the tapered region 130) defines a linear taper between the optical waveguide 105 and the contact region 110. As shown in fig. 3, the optical transition region 115 may be an octagon 305 that overlaps the optical waveguide 105. Other shapes of the optical transition region 115 (e.g., rectangular, diamond, hexagonal, etc.) with a linear taper are also possible. Further, although curved tapers and linear tapers are specifically discussed herein, tapered region 130 may have any other profile suitable for reducing optical losses caused by the intersection of optical waveguide 105 and contact region 110.

In some embodiments, optical waveguide 105, contact region 110, and/or optical transition region 115 may be integrally (monolithically) formed, but this is not required. For example, optical waveguide 105, contact region 110, and optical transition region 115 may be etched from a single layer of silicon or other suitable semiconductor material.

In some embodiments, the heating concentration of the device 100 may be controlled by having different portions of the device 100 have different dimensions and/or by differently doping different portions of the device 100. For example, a known etching process may be used to perform a partial etch of optical transition region 115 and/or optical waveguide 105 to provide a smaller electrical cross-section and, thus, a relatively greater electrical resistance as compared to other portion(s) of contact region 110. In another example, known doping processes may cause optical transition region 115 and/or optical waveguide 105 to have a relatively smaller doping level and, thus, a relatively greater resistance than other portion(s) of contact region 110.

Fig. 4 illustrates an exemplary doping profile 405 for a thermo-optic phase shifter, according to one embodiment. More specifically, the graph 400 shows a doping profile 405 relative to the long axis of the contact region 110 (aligned in the Y dimension, as shown).

In fig. 405, the optical transition region 115 and the optical waveguide 105 have a first doping level D1, and the portions 410-1, 410-2 of the contact region 110 that do not overlap the optical transition region 115 have a second doping level D2, the second doping level D2 being greater than the doping level D1. In this way, optical transition region 115 and optical waveguide 105 may have a relatively greater electrical resistance than portions 410-1, 410-2. When a current flows through the contact region 110, the heat generated in the vicinity of the optical waveguide 105 has a large concentration due to a relatively large resistance.

In some embodiments, the optical transition region 115 and/or the optical waveguide 105 may be sized differently than the portions 410-1, 410-2. For example, the optical transition region 115 and/or optical waveguide 105 has a smaller electrical cross-section than the portions 410-1, 410-2, which provides the optical transition region 115 and/or optical waveguide 105 with a relatively greater electrical resistance than the portions 410-1, 410-2. In one embodiment, the optical transition region 115 and/or the optical waveguide 105 may be partially etched to have a shorter height (e.g., in the Z-direction) than the portions 410-1, 410-2. Different sizing may be performed in addition to or instead of the different doping levels discussed above.

Further, while the different doping levels and/or heights have been described as two discrete levels or heights, alternative embodiments may include more than two discrete levels or heights, and/or one or more portions having a substantially continuous transition (e.g., a gradual transition) between the different doping levels or different heights.

Fig. 5 illustrates an exemplary apparatus 500 for conducting current along a length of an optical waveguide according to one embodiment. The apparatus 500 may be used in conjunction with other embodiments described herein. The device 500 includes an optical waveguide 105, a first contact region 110-1 and a second contact region 110-2, wherein the first contact region 110-1 intersects the optical waveguide 105 at a first intersection point and the second contact region 110-2 intersects the optical waveguide 105 at a second intersection point.

The contact area 110-1 is connected to the first contact 120-1 and the second contact area 110-2 is connected to the second contact 120-2. Contact 120-1 is disposed on a first side (in the positive Y-direction) of optical waveguide 105, and contact 120-2 is also disposed on the first side of optical waveguide 105. Alternatively, the contacts 120-1, 120-2 may be disposed on opposite sides of the optical waveguide 120. The contact regions 110-1, 110-2 may have substantially the same material composition, dimensions, and/or orientation with respect to the optical waveguide 105, but this is not required. For example, the extent of contact region 110-1 on the first side of optical waveguide 105 is depicted as being substantially the same as the extent of contact region 110-2 on the first side.

The voltage source 125 is configured to apply a voltage signal across the optical waveguide 105 through the contact regions 110-1, 110-2. The applied voltage signal causes a current 135 to pass between the contacts 120-1, 120-2 along the dimension of the optical waveguide 105. As shown, the dimension of the optical waveguide 105 is the length of the optical waveguide 105, which is substantially aligned with the X-axis. Due to the thermoelectric nature, the current 135 causes heating of the optical waveguide 105 such that the apparatus 100 is configured to receive a signal having a first phase Φ at the optical waveguide 105 ₁And transmits an optical signal having a second phase phi (the "optical input") ₂Wherein the second phase Φ ₂Different from the first phase phi ₁。

The apparatus 500 further comprises: a first optical transition region 115-1 extending between the optical waveguide 105 and the first contact region 110-1 in the vicinity of the first intersection point; and a second optical transition region 115-2 extending between the optical waveguide 105 and the second contact region 110-2 in the vicinity of the second intersection point. As shown, first optical transition region 115-1 and second optical transition region 115-2 extend beyond the respective intersection points, e.g., to the negative Y-direction of optical waveguide 105.

The first optical transition region 115-1 and the second optical transition region 115-2 each have a shape and size selected to mitigate optical losses that may typically occur due to the intersection of the respective contact regions 110-1, 110-2 with the optical waveguide 105. For example, the dimensions of each optical transition region 115-1, 115-2 may be selected based on one or more of the wavelength of the received first optical signal and the dimensions of the optical waveguide 105 (e.g., the width of the optical waveguide 105 in the Y-direction, the thickness of the semiconductor layers in the Z-direction). The first optical transition region 115-1 and the second optical transition region 115-2 each include one or more tapered regions.

Consistent with the discussion above, optical transition regions 115-1, 115-2, optical waveguide 105, and/or contact regions 110-1, 110-2 may have relative doping levels and/or dimensions to provide relative electrical resistance. In this way, resistive heat generated by the flow of current 135 may have a greater concentration near optical waveguide 105. A length L of the optical waveguide 105 is defined between the first intersection point and the second intersection point. In some embodiments, the length L is selected such that the optical waveguide 105 exhibits a desired resistance R between the first contact 110-1 and the second contact 110-2 _L。

FIG. 6 illustrates a plurality of layers including thermo-optic phase shifters in semiconductor layers according to one embodiment. For example, photonic platform 600 depicted in fig. 6 may be an SOI-based photonic platform. In accordance with the techniques discussed above, a thermo-optic phase shifter (e.g., apparatus 100, 500) may be formed in the semiconductor layer 615 of the photonic platform.

In photonic platform 600, dielectric layer 610 is partially disposed between base layer 605 and semiconductor layer 615. In an SOI-based example embodiment, the semiconductor layer 615 may be formed of silicon (Si) and the dielectric layer 610 may be formed of silicon dioxide (SiO) ₂) And base layer 605 may be formed of silicon. As shown, the dielectric layer 610 substantially surrounds the semiconductor layer 615. However, in other embodiments, the dielectric layer 610 is disposed entirely between the base layer 605 and the semiconductor layer 615.

In fig. 7, photonic platform 700 has region 705 removed from base layer 605. The removed region 705 typically overlaps at least a portion of the semiconductor layer 615. In some embodiments, the removed region overlaps at least one of an optical waveguide, a contact region, and an optical transition region formed in the semiconductor layer 615.

The material of the removed region 705 may be removed using backside etching techniques known in the art. In one example, a deep reactive ion etch or wet etch may be performed from the surface 710 of the base layer 605. In another example, a Complementary Metal Oxide Semiconductor (CMOS) etch process or a micro-electromechanical systems (MEMS) etch process may be performed from surface 710. Regardless of the backside etch process used, in some embodiments, the removed region 705 extends from a surface 710 of the base layer 605 to an opposite surface 715.

Removing material from the removed region 705 minimizes the dominant thermal radiation path from the thermo-optic phase shifter (in the semiconductor layer 615) to the base layer 605. Minimizing the thermal radiation path increases the efficiency of the thermo-optic phase shifter, in some cases by up to 10 times.

FIG. 8 illustrates an exemplary method 800 of phase shifting an optical signal according to one embodiment. The method 800 may be used in conjunction with other embodiments disclosed herein (e.g., the apparatus 100 of fig. 1 or the apparatus 500 of fig. 5).

The method 800 begins at block 805 by receiving an optical signal at a first end of an optical waveguide formed in a semiconductor layer and extending along a first axis at block 805. The first optical signal has a first phase.

At block 815, the modified optical signal is transmitted at a second end of the optical waveguide opposite the first end. The modified optical signal has a second phase different from the first phase. In some embodiments, sending the modified optical signal includes applying a voltage signal between a first contact region and a second contact region formed in the semiconductor layer away from the first axis. The application of the voltage signal conducts current along the dimensions of the optical waveguide to cause resistive heating of the optical waveguide. In some embodiments, the dimension is a width of the optical waveguide. In other embodiments, the dimension is a length of the optical waveguide. After block 815 is complete, method 800 ends.

In summary, embodiments include methods and associated apparatus for phase shifting an optical signal. A particular method includes receiving an optical signal having a first phase at a first end of an optical waveguide formed in a semiconductor layer and extending along a first axis. The method also includes transmitting the modified optical signal having a second phase at a second end of the optical waveguide opposite the first end, wherein the second phase is different from the first phase. Transmitting the modified optical signal comprises: a voltage signal is applied between a first contact region and a second contact region formed in the semiconductor layer away from the first axis. Applying a voltage signal causes a current to be conducted along the dimension of the optical waveguide. The current causes resistive heating of the optical waveguide and a desired phase shift between the first phase and the second phase.

In the foregoing, reference has been made to the embodiments presented in this disclosure. However, the scope of the present disclosure is not limited to the specifically described embodiments. Alternatively, any combination of the described features and elements (whether related to different embodiments or not) is contemplated to implement and practice the contemplated embodiments. Moreover, although embodiments disclosed herein may achieve advantages over other possible solutions or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the scope of the disclosure. Accordingly, the foregoing aspects, features, embodiments, and advantages are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s).

In view of the foregoing, the scope of the present disclosure is to be determined by the claims that follow.