阅读说明：本技术 一种波长可调谐的半导体激光器 (Semiconductor laser with tunable wavelength ) 是由 程远兵 陈光灿 毛远峰 于 2020-04-26 设计创作，主要内容包括：一种波长可调谐的半导体激光器,用于解决现有技术中激光器制作过程复杂的问题。该激光器可包括相互光耦合的第一光学谐振腔和第二光学谐振腔；第一光学谐振腔由第一半导体光波导和分别位于第一半导体光波导的两端的第一反射镜面和第二反射镜面形成,第二光学谐振腔由第二半导体光波导和分别位于第二半导体光波导的两端的第二反射镜面和第三反射镜面形成；第一光学谐振腔的腔长与第二光学谐振腔的腔长不同；第一反射镜和第三反射镜面中至少一个为部分发射镜面；第一半导体光波导与第二半导体光波导中的至少一个用于为对应的光学谐振腔提供回路增益。如此,不需要进行多次外延生长,制作激光器的过程比较简单。(A semiconductor laser with tunable wavelength is used for solving the problem that the manufacturing process of the laser is complex in the prior art. The laser may include a first optical resonant cavity and a second optical resonant cavity optically coupled to each other; the first optical resonant cavity is formed by a first semiconductor optical waveguide and a first reflector surface and a second reflector surface which are respectively positioned at two ends of the first semiconductor optical waveguide, and the second optical resonant cavity is formed by a second semiconductor optical waveguide and a second reflector surface and a third reflector surface which are respectively positioned at two ends of the second semiconductor optical waveguide; the cavity length of the first optical resonant cavity is different from the cavity length of the second optical resonant cavity; at least one of the first reflector and the third reflector is a partial emission reflector; at least one of the first semiconductor optical waveguide and the second semiconductor optical waveguide is used for providing loop gain for the corresponding optical resonant cavity. Therefore, multiple times of epitaxial growth are not needed, and the process of manufacturing the laser is simpler.)

1. A wavelength tunable semiconductor laser comprising a first optical resonator and a second optical resonator optically coupled to each other; the first optical resonant cavity is formed by a first semiconductor optical waveguide and a first reflecting mirror surface and a second reflecting mirror surface which are respectively positioned at two ends of the first semiconductor optical waveguide, and the second optical resonant cavity is formed by a second semiconductor optical waveguide and a second reflecting mirror surface and a third reflecting mirror surface which are respectively positioned at two ends of the second semiconductor optical waveguide;

wherein the cavity length of the first optical resonant cavity is different from the cavity length of the second optical resonant cavity; at least one of the first mirror surface and the third mirror surface is a partially reflecting mirror surface; at least one of the first semiconductor optical waveguide and the second semiconductor optical waveguide is used for providing loop gain for a corresponding optical resonant cavity.

2. The laser of claim 1, wherein the first mirror is a Sagnac loop mirror waveguide; or, a fully reflective multimode interferometer MMI reflective waveguide;

the second reflector surface is the Sagnac ring mirror surface waveguide; or, a trench waveguide etched back;

the third reflector is the Sagnac loop mirror waveguide; or, a totally reflecting MMI reflecting waveguide;

the Sagnac ring mirror surface waveguide consists of 2 x 2 directional couplers with two end faces connected, or is formed by a 2 x 2MMI waveguide with one end face connected; the total-reflection MMI reflection waveguide is formed by connecting a 1 × 1MMI input waveguide with one end of a half-cavity-length multimode waveguide or connecting a 2 × 1MMI input waveguide with one end of the half-cavity-length multimode waveguide, the other end of the multimode waveguide comprises two mutually perpendicular end faces, and the included angle between each of the two mutually perpendicular end faces and the input waveguide is 45 degrees.

3. The laser of claim 1 or 2, wherein the first mirror and the third mirror are both the Sagnac loop mirror waveguide;

a direction of decrease in width of an end of the first mirror surface connected to the first semiconductor optical waveguide is opposite to a direction of decrease in width of an end of the first semiconductor optical waveguide connected to the first mirror surface;

the direction of decrease in the width of the end of the third mirror surface connected to the second semiconductor optical waveguide is opposite to the direction of decrease in the width of the end of the second semiconductor optical waveguide connected to the third mirror surface.

4. The laser of claim 3, wherein the lengths of both ends of the first semiconductor optical waveguide, which are respectively connected with the first reflecting mirror surface and the second reflecting mirror surface, are greater than or equal to 10um and less than or equal to 200 um;

the second semiconductor optical waveguide with the second mirror surface with the length at the both ends that the third mirror surface is connected respectively all is more than or equal to 10um, and less than or equal to 200 um.

5. The laser of any of claims 1 to 4, wherein the first semiconductor optical waveguide and the second semiconductor optical waveguide are both group III-V material optical waveguides, and the first mirror surface, the second mirror surface, and the third mirror surface are all silicon optical waveguides.

6. The laser of claim 5, wherein the heterogeneous integration of the group III-V material optical waveguide and the silicon optical waveguide comprises wafer-to-wafer bonding; alternatively, wafer-to-wafer bonding.

7. The laser of any of claims 1 to 4, wherein the first semiconductor optical waveguide, the second semiconductor optical waveguide, the first mirror surface, the second mirror surface, and the third mirror surface are all group III-V material optical waveguides;

the first semiconductor optical waveguide and the second semiconductor optical waveguide respectively comprise a P-InGaAs layer/a P-InP cladding layer/an active layer/an N-InP layer, and the active layer is made of multiple quantum well materials or quantum dot materials; the first reflector surface and the third reflector comprise a P-InGaAs layer/P-InP cladding layer/passive core layer/N-InP layer, and the second reflector surface is a groove waveguide deeply etched on the first semiconductor optical waveguide or the second semiconductor optical waveguide.

8. The laser of claim 7, wherein the length of the deep etched trench waveguide is an odd multiple of one quarter of a lasing wavelength, and the depth of the deep etched trench waveguide is less than or equal to the sum of the thicknesses of the P-InGaAs layer and the P-InP cladding layer.

9. The laser of any of claims 1 to 8, wherein the cavity length of the first optical resonant cavity is determined according to the length of the first mirror surface, the length of the second mirror surface, and the length of the first semiconductor optical waveguide;

the cavity length of the second optical resonant cavity is determined according to the length of the second reflecting mirror surface, the length of the third reflecting mirror surface and the length of the second semiconductor optical waveguide.

10. The laser of any of claims 1 to 9, wherein an optical coupling efficiency of the first optical resonant cavity and the second optical resonant cavity is determined based on a reflectivity of the second mirrored surface; wherein the reflectivity of the second reflector surface is greater than 0 and less than 100%.

11. The laser of any one of claims 1 to 10, wherein the first optical waveguide is formed by varying a first current injected into the first optical semiconductor waveguide or varying a temperature of the first optical semiconductor waveguide; and/or by varying a second current injected into the second semiconductor optical waveguide or varying a temperature of the second semiconductor optical waveguide; the resonance wavelength of the first optical resonant cavity and the resonance wavelength of the second optical resonant cavity are overlapped in the respective gain spectrum range and only one wavelength is overlapped.

12. The laser of any one of claims 1 to 11, further comprising a first electrode and/or a second electrode;

the first electrode is used for injecting a first current into the first semiconductor optical waveguide;

the second electrode is used for injecting a second current into the second semiconductor optical waveguide;

wherein the first current is greater than a current threshold of the first optical resonant cavity, and/or the second current is greater than a current threshold of the second optical resonant cavity.

13. The laser of claim 12, further comprising a first thin film resistor and/or a second thin film resistor, wherein the first thin film resistor is provided with a third electrode and a fourth electrode at two ends thereof, and the second thin film resistor is provided with a fifth electrode and a sixth electrode at two ends thereof;

the third electrode and the fourth electrode are used for injecting a third current into the first thin film resistor, and the third current is used for carrying out thermal regulation on the first thin film resistor;

the fifth electrode and the sixth electrode are configured to inject a fourth current into the second thin-film resistor, where the fourth current is used to thermally adjust the second thin-film resistor.

Technical Field

The application relates to the technical field of lasers, in particular to a semiconductor laser with tunable wavelength.

Background

The wavelength tunable laser is an important photoelectric device and can be widely applied to the fields of optical communication, sensing, biological detection, computer systems and the like. In optical communications, Wavelength Division Multiplexer (WDM) networks, Passive Optical Networks (PONs), Optical Distribution Networks (ODNs), and the like all require that the wavelength of the output of the light source is continuously tunable or quasi-continuously tunable, and the light source can keep single-mode operation within the wavelength tunable range, so a wavelength tunable laser is usually selected as the light source, where the wavelength tunable laser refers to a laser whose wavelength can be changed according to needs.

Tunable lasers such as Sampled Grating Distributed Bragg Reflector (SGDBR), super-structured grating distributed bragg reflector (SSGDBR), digital super-mode distributed bragg reflector (DSDBR), bragg reflector (DBR), etc. all have the characteristics of quasi-continuous wide-wavelength tuning and single-mode output, and have been successfully applied to optical communications.

However, these lasers are complex to fabricate, and usually include multiple regions, and the material band gap wavelength of each region is different, and complex monolithic integration techniques such as butt growth are required to fabricate the lasers, so the chip fabrication cost is high; on the other hand, the operating conditions of each region need to be strictly matched to realize stable wavelength tuning, i.e. the wavelength tuning of the laser is also complicated.

Disclosure of Invention

The application provides a semiconductor laser with tunable wavelength, which is used for solving the problem that the manufacturing process of the laser is complex in the prior art.

In a first aspect, the present application provides a wavelength tunable semiconductor laser that may include a first optical resonant cavity and a second optical resonant cavity optically coupled to each other; the first optical resonant cavity is formed by a first semiconductor optical waveguide and a first reflector surface and a second reflector surface which are respectively positioned at two ends of the first semiconductor optical waveguide, and the second optical resonant cavity is formed by a second semiconductor optical waveguide and a second reflector surface and a third reflector surface which are respectively positioned at two ends of the second semiconductor optical waveguide; wherein the cavity length of the first optical resonant cavity is different from the cavity length of the second optical resonant cavity; at least one of the first reflector and the third reflector is a partial emission reflector; at least one of the first semiconductor optical waveguide and the second semiconductor optical waveguide is used for providing loop gain for the corresponding optical resonant cavity.

Based on the scheme, the semiconductor laser with tunable wavelength comprises an optical resonant cavity formed by a semiconductor optical waveguide and reflector waveguides respectively positioned at two ends of the semiconductor optical waveguide, a grating is not needed, complex butt growth or grating covering and other multiple epitaxial growth are not needed, and the process for manufacturing the laser is simpler. Furthermore, the cavity length of the first optical resonant cavity is different from that of the second optical resonant cavity, the cavity length can be accurately positioned, and at least one of the first semiconductor optical waveguide and the second semiconductor optical waveguide can provide loop gain for the corresponding optical resonant cavity, so that the laser can output stable single-mode laser.

In one possible implementation, the first mirror may be a Sagnac loop mirror waveguide, or a fully reflective multimode interferometer (MMI) reflective waveguide; the second reflecting mirror surface is a Sagnac ring mirror surface waveguide or a deep etched groove waveguide; the third reflector is a Sagnac ring reflector waveguide, or a fully reflective MMI reflector waveguide. The Sagnac ring mirror surface waveguide consists of 2 x 2 directional couplers with two end faces connected, or is formed by a 2 x 2MMI waveguide with one end face connected; the total-reflection MMI reflection waveguide is formed by connecting a 1 × 1MMI input waveguide with one end of a half-cavity-length multimode waveguide or connecting a 2 × 1MMI input waveguide with one end of the half-cavity-length multimode waveguide, the other end of the multimode waveguide comprises two mutually perpendicular end faces, and the included angle between each of the two mutually perpendicular end faces and the input waveguide is 45 degrees.

Illustratively, the first mirror facet, the second mirror facet, and the third mirror facet may each be Sagnac loop mirror waveguides; or the first reflector surface and the third reflector surface are both Sagnac ring mirror surface waveguides, and the second reflector surface is a deep etched groove waveguide; or the first reflector surface and the third reflector surface are both MMI reflective waveguides with total reflection, and the second reflector surface is a trench waveguide with deep etching; or the first reflector surface and the second reflector surface are Sagnac ring mirror surface waveguides, and the third reflector surface is a total-reflection MMI reflection waveguide; or the third reflector surface and the second reflector surface are Sagnac ring reflector surface waveguides, and the first reflector surface is a total-reflection MMI reflection waveguide; or the first reflector surface is a Sagnac ring reflector surface waveguide, the second reflector surface waveguide is a deep etched groove waveguide, and the third reflector surface is a total-reflection MMI reflector waveguide; or the first reflector is a total-reflection MMI reflector waveguide, the second reflector is a deep-etched groove waveguide, and the third reflector is a Sagnac ring reflector waveguide.

When the first reflecting mirror surface, the second reflecting mirror surface and the third reflecting mirror surface are silicon optical waveguides, the characteristic of low loss of the silicon optical waveguides can be fully utilized, the transmission loss of light in the mirror surface waveguides is reduced, and therefore narrow-line output can be achieved. When the first reflecting mirror surface, the second reflecting mirror surface and the third reflecting mirror surface are made of III-V material optical waveguides, the gain waveguides are also made of III-V material, so that the laser can be manufactured by an InP-based monolithic integration process, and the yield is high. That is to say, the first mirror surface, the second mirror surface and the third mirror surface in the application can be processed and formed through a common photoetching process, electron beam exposure is not needed, processes such as high-precision cavity surface cleavage are not needed, multiple times of epitaxial growth is not needed, and the reflection efficiency is easy to design.

In one possible implementation, the first mirror facet and the third mirror facet are both silicon light Sagnac loop mirror waveguides; the width of one end of the first reflector surface connected with the first semiconductor optical waveguide is reduced in a direction opposite to the width of one end of the first semiconductor optical waveguide connected with the first reflector surface; the direction of decrease in the width of the end of the third mirror surface connected to the second semiconductor optical waveguide is opposite to the direction of decrease in the width of the end of the second semiconductor optical waveguide connected to the third mirror surface.

In another possible implementation, the first mirror facet, the second mirror facet, and the third mirror facet are Sagnac loop mirror waveguides; the width of one end of the first reflector surface connected with the first semiconductor optical waveguide is reduced in a direction opposite to the width of one end of the first semiconductor optical waveguide connected with the first reflector surface; the width of the end of the second reflector surface connected with the first semiconductor optical waveguide is reduced in a direction opposite to the width of the end of the first semiconductor optical waveguide connected with the second reflector surface; the width of the end of the second reflecting mirror surface connected with the second semiconductor optical waveguide is reduced in a direction opposite to the width of the end of the second semiconductor optical waveguide connected with the second reflecting mirror surface; the direction of decrease in the width of the end of the third mirror surface connected to the second semiconductor optical waveguide is opposite to the direction of decrease in the width of the end of the second semiconductor optical waveguide connected to the third mirror surface.

The light coupling efficiency between the semiconductor optical waveguide and the reflecting mirror surface can be improved by reversing the direction of decrease in the width of the end of the semiconductor optical waveguide connected to the reflecting mirror to the direction of decrease in the width of the end of the reflecting mirror connected to the semiconductor optical waveguide.

In a possible implementation manner, the lengths of two ends of the first semiconductor optical waveguide, which are respectively connected with the first reflecting mirror surface and the second reflecting mirror surface, are both greater than or equal to 10um and less than or equal to 200 um; the lengths of two ends of the second semiconductor optical waveguide, which are respectively connected with the second reflecting mirror surface and the third reflecting mirror surface, are both more than or equal to 10um and less than or equal to 200 um.

In one possible implementation, the first semiconductor optical waveguide and the second semiconductor optical waveguide are both III-V material optical waveguides, and the first mirror surface, the second mirror surface, and the third mirror surface are all silicon optical waveguides.

In one possible implementation, the heterogeneous integration of III-V material optical waveguides with silicon optical waveguides includes wafer-wafer bonding; alternatively, wafer-to-wafer bonding.

The adiabatic coupling can be realized through wafer-wafer bonding or wafer-wafer bonding, and the adiabatic coupling helps to avoid changing the refractive index of the first semiconductor optical waveguide and/or the second semiconductor optical waveguide, thereby helping to avoid causing the cavity length of the first optical resonant cavity to change and/or the cavity length of the second optical resonant cavity to change, so that the cavity lengths of the two optical resonant cavities can be accurately controlled, and the laser can be helped to output stable single-mode laser.

In one possible implementation, the first semiconductor optical waveguide, the second semiconductor optical waveguide, the first mirror surface, the second mirror surface, and the third mirror surface are all group III-V material optical waveguides. The first semiconductor optical waveguide and the second semiconductor optical waveguide respectively comprise a P-InGaAs layer/a P-InP cladding layer/an active layer/an N-InP layer, and the active layer is made of multiple quantum well materials or quantum dot materials; the first reflector surface and the third reflector surface comprise a P-InGaAs layer/a P-InP cladding layer/a passive core layer/an N-InP layer, and the second reflector surface is a groove waveguide deeply etched on the first semiconductor optical waveguide or the second semiconductor optical waveguide.

Further optionally, the length of the deep-etched trench waveguide is an odd multiple of one quarter of the lasing wavelength, and the depth of the deep-etched trench waveguide is less than or equal to the sum of the thicknesses of the P-InGaAs layer and the P-InP cladding layer.

The length of the trench waveguide which is deeply etched is odd times of one quarter of the lasing wavelength, so that the influence on the power and the lasing wavelength of the laser can be avoided as much as possible; the depth of the trench waveguide is not etched to the active layer, which helps to prevent the deep etching from affecting the lifetime of the light emitted by the active layer.

In the application, the cavity length of the first optical resonant cavity is determined according to the length of the first reflecting mirror surface, the length of the second reflecting mirror surface and the length of the first semiconductor optical waveguide; the cavity length of the second optical resonant cavity is determined based on the length of the second mirror surface, the length of the third mirror surface, and the length of the second semiconductor optical waveguide.

Because the Sagnac loop mirror waveguide can be manufactured by photoetching, the cavity length of the optical resonant cavity can be accurately controlled by designing the positions of the first reflecting mirror surface, the second reflecting mirror surface and the third reflecting mirror surface, generally, the cavity length error of the optical resonant cavity with the Sagnac loop mirror surface as the reflecting mirror surface is about +/-1 um and is far less than the cavity length error (more than +/-10 um) of the optical resonant cavity formed by forming the mirror surface according to the natural cleavage surface of a semiconductor wafer in the prior art, and therefore, when the first reflecting mirror surface is the Sagnac loop mirror waveguide, the cavity length error of the optical resonant cavity of the laser can be favorably reduced. That is, the cavity length of the first optical resonator and the cavity length of the second optical resonator can be defined by Sagnac toroidal mirror, and therefore, the cavity length of the first optical resonator and the cavity length of the second optical resonator can be accurately controlled, thereby contributing to the improvement of the stability of the output mode of the laser.

In one possible implementation, if the first mirror facet is a first Sagnac loop-mirror waveguide, the second mirror facet is a second Sagnac loop-mirror waveguide, and the third mirror facet is a third Sagnac loop-mirror waveguide, the cavity length of the first optical resonator cavity is equal to a sum of half a length of the first Sagnac loop-mirror waveguide, half a length of the first semiconductor optical waveguide, and half a length of the second Sagnac loop-mirror waveguide, and the cavity length of the second optical resonator cavity is equal to a sum of half a length of the second Sagnac loop-mirror waveguide, half a length of the second semiconductor optical waveguide, and half a length of the third Sagnac loop-mirror waveguide.

In another possible implementation manner, if the first mirror surface is a first Sagnac loop mirror surface waveguide, the second mirror surface is a deep-etched trench waveguide, and the third mirror surface is a third Sagnac loop mirror surface waveguide, the cavity length of the first optical resonant cavity is equal to half of the length of the first Sagnac loop mirror surface waveguide, half of the length of the deep-etched trench waveguide, and the length of the first semiconductor optical waveguide, and the cavity length of the second optical resonant cavity is equal to half of the length of the deep-etched trench waveguide, half of the length of the third Sagnac loop mirror surface waveguide, and the length of the second semiconductor optical waveguide.

In another possible implementation manner, if the first reflector surface is a first total-reflection MMI reflector waveguide, the second reflector surface is a deep-etched trench waveguide, and the third reflector surface is a third total-reflection MMI reflector waveguide, the cavity length of the first optical resonant cavity is equal to the length of the first total-reflection MMI reflector waveguide, the length of the deep-etched trench waveguide, and the length of the first semiconductor optical waveguide, and the cavity length of the second optical resonant cavity is equal to the length of the deep-etched trench waveguide, the length of the third total-reflection MMI reflector waveguide, and the length of the second semiconductor optical waveguide.

In one possible implementation, the optical coupling efficiency of the first optical resonant cavity and the second optical resonant cavity is determined according to the reflectivity of the second reflecting mirror surface; wherein the reflectivity of the second reflector surface is greater than 0 and less than 100%.

In the present application, the first semiconductor optical waveguide may be formed by changing a first current injected into the first semiconductor optical waveguide or changing a temperature of the first semiconductor optical waveguide; and/or by varying a second current injected into the second semiconductor optical waveguide or varying a temperature of the second semiconductor optical waveguide; the resonant wavelength of the first optical resonator and the resonant wavelength of the second optical resonator are made to coincide with each other in the respective gain spectrum ranges, with only one wavelength. In this way, wavelength tuning of the laser can be achieved.

Nine ways of making the resonance wavelength of the first optical resonator and the resonance wavelength of the second optical resonator coincide with each other within the respective gain spectrum range and only one wavelength are exemplarily shown as follows.

In the manner 1, the magnitude of the first current injected into the first semiconductor optical waveguide can be changed.

Mode 2, the temperature of the first semiconductor optical waveguide can be changed.

In mode 3, the magnitude of the second current injected into the second semiconductor waveguide can be changed.

Mode 4, the temperature of the second semiconductor optical waveguide can be changed.

Mode 5, the magnitude of the first current injected into the first semiconductor optical waveguide and the magnitude of the second current injected into the second semiconductor optical waveguide can be changed, that is, mode 1 and mode 3 can be combined.

Mode 6, mode 2 and mode 4 can be combined by changing the temperature of the first semiconductor optical waveguide and changing the temperature of the second semiconductor optical waveguide.

Mode 7 can be combined by changing the magnitude of the first current injected into the first semiconductor optical waveguide and changing the temperature of the second semiconductor optical waveguide, i.e., mode 1 and mode 4.

Mode 8, mode 2 and mode 3 can be combined by changing the temperature of the first semiconductor optical waveguide and changing the magnitude of the second current injected into the second semiconductor optical waveguide.

Mode 9, mode 2 and mode 4 can be combined by changing the temperature of the first semiconductor optical waveguide and changing the temperature of the second semiconductor optical waveguide.

The above-described modes 1, 3, and 5 are electrical tuning; the above-described modes 2, 4, and 6 are thermal tuning; the above-described modes 7, 8, and 9 are combinations of electrical tuning and thermal tuning.

In one possible implementation, the laser further comprises a first electrode and/or a second electrode; the first electrode is used for injecting a first current into the first semiconductor optical waveguide, and the first current is larger than the current threshold value of the first optical resonant cavity; the second electrode is used for injecting a second current into the second semiconductor optical waveguide, and the second current is larger than the current threshold value of the second optical resonant cavity. In this way, at least one of the first semiconductor optical waveguide and the second semiconductor optical waveguide can be made to provide gain for the loop, i.e., at least one of the first semiconductor optical waveguide and the second semiconductor optical waveguide is a gain waveguide.

In a possible implementation manner, the laser further includes a first thin film resistor and/or a second thin film resistor, where two ends of the first thin film resistor are respectively provided with a third electrode and a fourth electrode, and two ends of the second thin film resistor are respectively provided with a fifth electrode and a sixth electrode; the third electrode and the fourth electrode are used for injecting a third current into the first thin film resistor, and the third current is used for carrying out thermal regulation on the first thin film resistor; the fifth electrode and the sixth electrode are used for injecting a fourth current into the second thin film resistor, and the fourth current is used for carrying out thermal regulation on the second thin film resistor. In this way, wavelength tuning of the laser can be achieved by means of thermal tuning.

Drawings

Fig. 1a is a schematic structural diagram of an SGDBR laser in the prior art;

FIG. 1b is a schematic diagram of a prior art Y-DBR laser;

fig. 2 is a schematic structural diagram of a wavelength tunable semiconductor laser provided herein;

FIG. 3a is a schematic diagram of a Sagnac ring mirrored waveguide according to the present application;

FIG. 3b is a schematic diagram of another Sagnac ring mirrored waveguide configuration provided herein;

FIG. 3c is a schematic diagram of a fully reflective MMI waveguide structure according to the present application;

FIG. 3d is a schematic diagram of another fully reflective MMI reflective waveguide structure provided herein;

FIG. 4 is a schematic structural diagram of an optical waveguide of a III-V material provided herein;

FIG. 5 is a schematic structural view of an optical waveguide of another III-V material provided herein;

FIG. 6a is a schematic diagram of two optical resonators coupled to each other according to the present application;

FIG. 6b is a schematic diagram illustrating the structure of the junction of a semiconductor optical waveguide and a Sagnac toroidal waveguide according to the present application;

FIG. 6c is a graph illustrating the relationship between optical coupling efficiency and length according to the present application;

FIG. 6d is a schematic diagram of the cavity length of another two optical resonant cavities coupled to each other as provided herein;

FIG. 7a is a schematic diagram of another structure of two optical resonators coupled to each other according to the present application;

FIG. 7b is a schematic diagram illustrating the cavity length of an optical resonator according to the present application;

FIG. 8a is a schematic diagram of another two optical resonators coupled to each other according to the present application;

FIG. 8b is a schematic diagram of the cavity length of another optical resonator provided herein;

fig. 9a is a schematic structural diagram of a laser provided in the present application;

FIG. 9b is a schematic diagram of another laser configuration provided herein;

FIG. 9c is a schematic diagram of another laser structure provided in the present application;

FIG. 10 is a schematic diagram of a laser device for outputting laser light according to the present disclosure;

FIG. 11 is a schematic diagram of another laser configuration provided herein;

FIG. 12 is a schematic diagram of another laser configuration provided herein;

FIG. 13 is a schematic diagram of another laser provided by the present application for outputting laser light;

FIG. 14 is a schematic diagram of another laser structure provided in the present application;

fig. 15 is a schematic diagram of the laser output of another laser provided in the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more clear, the present application will be further described in detail with reference to the accompanying drawings.

Currently, tunable lasers widely used include SGDBR lasers, Y-DBR lasers, and the like. As shown in fig. 1a, the SGDBR laser includes a front mirror, a rear mirror, a gain section, a phase section, and an amplification section, and since the optical power of the SGDBR laser is small, the optical power of the SGDBR laser can be increased by a Semiconductor Optical Amplifier (SOA) in order to increase the optical power of the laser. FIG. 1b shows a four-section Y-DBR laser. The Y-DBR laser includes a front mirror, a back mirror, a gain section, a phase section, and a multimode interferometer (MMI) waveguide section. The band gaps of the materials required for the five segments (i.e. the front mirror, the back mirror, the gain region, the phase region and the amplifying region) in fig. 1a are different, and at least 5 times of material epitaxial growth is required, so that the laser is complicated to manufacture and has low yield. The epitaxial growth means that a single crystal layer with certain requirements and the same crystal orientation as the substrate grows on a single crystal substrate, and the single crystal layer is just like the original crystal which extends outwards by a section. The laser shown in fig. 1b also requires at least 4 times of material epitaxial growth, and there are problems that the manufacturing process of the laser is complicated and the yield is low.

In view of the above, the present application proposes a wavelength tunable semiconductor laser. Fig. 2 is a schematic structural diagram of a wavelength tunable semiconductor laser according to the present application. The wavelength tunable semiconductor laser may include a first optical resonant cavity and a second optical resonant cavity coupled to each other. The first optical resonant cavity is formed by a first semiconductor optical waveguide and a first reflector surface and a second reflector surface which are respectively positioned at two ends of the first semiconductor optical waveguide, and the second optical resonant cavity is formed by a second semiconductor optical waveguide and a second reflector surface and a third reflector surface which are respectively positioned at two ends of the second semiconductor optical waveguide; the cavity length of the first optical resonant cavity is different from the cavity length of the second optical resonant cavity, at least one of the first reflector surface and the third reflector surface is a partial reflector surface, at least one of the first semiconductor optical waveguide and the second semiconductor optical waveguide is used for providing gain for the corresponding optical resonant cavity, namely at least one of the first semiconductor optical waveguide and the second semiconductor optical waveguide is a gain waveguide.

In a possible implementation manner, when the first reflecting mirror surface is a partial reflecting mirror surface and the third reflecting mirror surface is a total reflecting mirror surface, the first reflecting mirror surface may also be used to output laser light; when the third reflecting mirror surface is a partial reflecting mirror surface and the first reflecting mirror surface is a total reflecting mirror surface, the third reflecting mirror surface is used for outputting laser; when both the first mirror surface and the third mirror surface are partial mirror surfaces, one of them may be selected for outputting laser light. That is, at least one of the first mirror surface and the third mirror surface is a partially reflective mirror surface. The term "partially reflecting mirror surface" means that the reflectivity of the reflecting mirror surface is greater than 0 and less than 100%. For example, the second mirrored surface is a partially mirrored surface, meaning that the second mirrored surface has a reflectivity greater than 0 and less than 100% (e.g., 80%, 85%, etc.); for another example, the first mirror surface is a partial mirror surface, which means that the reflectivity of the first mirror surface is greater than 0 and less than 100%; for another example, the third mirror surface is a partial mirror surface, which means that the reflectivity of the third mirror surface is greater than 0 and less than 100%.

In one possible implementation, the cavity length of the first optical resonant cavity is greater than the cavity length of the second optical resonant cavity; alternatively, the cavity length of the first optical resonant cavity is smaller than the cavity length of the second optical resonant cavity.

It should be noted that the first optical resonant cavity and the second optical resonant cavity coupled to each other refer to: light from the first optical cavity may be transmitted to the second optical cavity, and light from the second optical cavity may also be transmitted to the first optical cavity. Since the first optical resonant cavity and the second optical resonant cavity are coupled to each other, the second reflective mirror surface may be a partially reflective mirror surface, or the second reflective mirror surface may have a wavelength selective characteristic, wherein the wavelength selective characteristic means that a part of the wavelength of light is allowed to pass completely, and another part of the wavelength of light is reflected completely (i.e., not allowed to pass completely).

Based on the semiconductor laser with tunable wavelength, the included optical resonant cavity is formed by the semiconductor optical waveguide and the reflector waveguides respectively positioned at two ends of the semiconductor optical waveguide, no grating is needed, complex butt growth or grating covering and other multiple epitaxial growth are not needed, and the process for manufacturing the laser is simpler. Furthermore, the cavity length of the first optical resonant cavity is different from that of the second optical resonant cavity, the cavity length can be accurately positioned, and at least one of the first semiconductor optical waveguide and the second semiconductor optical waveguide can provide loop gain for the corresponding optical resonant cavity, so that the laser can output stable single-mode laser.

The following describes the respective structures shown in fig. 2 to give an exemplary embodiment.

First, reflecting mirror surface

In this application, the mirror surfaces may include a first mirror surface, a second mirror surface, and a third mirror surface.

In one possible implementation, the first mirror may be a Sagnac loop mirror waveguide; or it may be a fully reflective MMI reflective waveguide. It should be understood that Sagnac loop mirrored waveguides may allow a portion of wavelengths of light to pass completely through and another portion of wavelengths of light to be fully reflected (i.e., not allowed to pass at all).

Fig. 3a is a schematic diagram of a Sagnac loop mirror waveguide according to the present invention. The Sagnac loop mirror waveguide consists of a 2 x 2 directional coupler connected at both end faces. A 2 x 2 directional coupler refers to a four-port device comprising two input waveguides and two output waveguides, which are connected by two mutually parallel waveguides, and is generally used for combining and splitting. And the two waveguides with unconnected end surfaces are used as a reflecting waveguide and a transmission waveguide of light.

Fig. 3b is a schematic diagram of another Sagnac loop mirrored waveguide configuration provided herein. The Sagnac ring mirror waveguide consists of a 2 × 2MMI waveguide with two input/output waveguide end faces connected on the same side. The 2 x 2MMI waveguide is a four-port device comprising two input waveguides and two output waveguides, the input waveguides and the output waveguides are connected by a multimode waveguide, usually used for wave combination and wave division or wavelength multiplexing/demultiplexing, the Sagnac ring mirror waveguide formed by the 2 x 2MMI waveguides connected by the two input/output waveguide end faces on the same side, the two unconnected waveguides are used as a light reflecting waveguide and a light transmitting waveguide.

Fig. 3c is a schematic diagram of a structure of a total reflection MMI reflection waveguide provided in the present application. The total-reflection MMI reflection waveguide is formed by connecting a 1 × 1MMI input waveguide with a multimode waveguide of half the cavity length. (ii) a One end of the multimode waveguide is connected with the 1 × 1MMI input waveguide, the other end of the multimode waveguide comprises two mutually perpendicular end faces, and the included angle between each of the two mutually perpendicular end faces and the MMI input waveguide is 45 degrees.

Based on the totally reflected MMI reflective waveguide shown in fig. 3c, light is input from the MMI input waveguide, enters the multimode waveguide, is totally reflected by two mutually perpendicular reflective surfaces of the multimode waveguide, and is output from the MMI input waveguide, where the input waveguide is also an output waveguide, and the input waveguide and the output waveguide are the same.

Fig. 3d shows a schematic diagram of another structure of a total-reflective MMI reflective waveguide according to the present application. The total-reflection MMI reflection waveguide is formed by connecting a 2 × 1MMI input waveguide with a multimode waveguide of half the cavity length. A 2 x 1MMI input waveguide refers to a three-port device comprising two input waveguides and an output waveguide, the input and output waveguides being connected by a multimode waveguide, typically for combining and splitting or wavelength multiplexing/demultiplexing; one end of the multimode waveguide is connected with the 2 x 1MMI input waveguide, the other end of the multimode waveguide comprises two mutually perpendicular end faces, and the included angle between each end face of the two mutually perpendicular end faces and the input waveguide is 45 degrees.

Based on the totally reflected MMI reflective waveguide shown in fig. 3d, light is input from one of the input waveguides of the MMI, enters the multimode waveguide, is totally reflected by two mutually perpendicular reflective surfaces of the multimode waveguide, and is output from the two input waveguides of the MMI, where the input waveguides are also output waveguides at the same time.

It should be noted that the cavity length of the multimode waveguide in fig. 3c and 3d is half of the cavity length of the complete multimode waveguide. The multimode waveguide with half cavity length and the structure of the virtual line part form a complete multimode waveguide, and light can enter the multimode waveguide from the input waveguide on the left side and then is output from the output waveguide on the right side after passing through the multimode waveguide.

In one possible implementation, the third mirror may be a Sagnac ring mirror waveguide; or it may be a fully reflective MMI reflective waveguide. Wherein, the Sagnac loop mirror waveguide and the total reflection MMI waveguide can be referred to the related descriptions above, and the description is not repeated here.

In one possible implementation, the second mirror may be a Sagnac loop mirror waveguide; or may be a deep etched trench waveguide. When the second reflector is a Sagnac loop mirror waveguide, reference may be made to the above description of the Sagnac loop mirror waveguide, and details are not repeated here.

Illustratively, the first mirror facet, the second mirror facet, and the third mirror facet may each be Sagnac loop mirror waveguides; or the first reflector surface and the third reflector surface are both Sagnac ring mirror surface waveguides, and the second reflector surface is a deep etched groove waveguide; or the first reflector surface and the third reflector surface are both MMI reflective waveguides with total reflection, and the second reflector surface is a trench waveguide with deep etching; or the first reflector surface and the second reflector surface are Sagnac ring mirror surface waveguides, and the third reflector surface is a total-reflection MMI reflection waveguide; or the third reflector surface and the second reflector surface are Sagnac ring reflector surface waveguides, and the first reflector surface is a total-reflection MMI reflection waveguide; or the first reflector surface is a Sagnac ring reflector surface waveguide, the second reflector surface waveguide is a deep etched groove waveguide, and the third reflector surface is a total-reflection MMI reflector waveguide; or the first reflector is a total-reflection MMI reflector waveguide, the second reflector is a deep-etched groove waveguide, and the third reflector is a Sagnac ring reflector waveguide.

In the present application, the first mirror surface, the second mirror surface and the third mirror surface may all be silicon optical waveguides, such as silicon-on-insulator (SOI) or silicon nitride (SiN) or silicon-on-insulator (SiN-on-SOI); or the first reflector surface, the second reflector surface and the third reflector surface can be all optical waveguides made of III-V materials; or the first reflecting mirror surface and the third reflecting mirror surface are silicon optical waveguides, and the second reflecting mirror surface is III-V material optical waveguides. When the second reflecting surface is an optical waveguide made of III-V material, the second reflecting surface may be a trench etched back into the first semiconductor optical waveguide or the second semiconductor optical waveguide.

Fig. 4 is a schematic structural diagram of an optical waveguide made of III-V materials according to the present application. The group III-V material optical waveguide may be a first mirror, or a second mirror or a third mirror. The III-V material optical waveguide comprises the following components in sequence from top to bottom: a P-doped-indium gallium arsenide (P-InGaAs) layer, a P-doped-indium phosphide (P-InP) cladding (cladding) layer, a passive core layer, and an N-doped-indium phosphide (N-InP) layer. Further, the passive core layer may alternatively be composed of InGaAsP or InGaAlAs bulk material or multiple quantum well material with a bandgap wavelength smaller than that of the input waveguide.

When the first reflecting mirror surface, the second reflecting mirror surface and the third reflecting mirror surface are silicon optical waveguides, the characteristic of low loss of the silicon optical waveguides can be fully utilized, the reduction of optical transmission loss is facilitated, and then narrow-line output can be realized. Furthermore, when the first reflecting mirror surface, the second reflecting mirror surface and the third reflecting mirror surface are made of III-V material optical waveguides, the gain waveguides are also made of III-V material, so that the laser can be manufactured by an InP-based monolithic integration process, and the yield is high. That is to say, the first mirror surface, the second mirror surface and the third mirror surface in the application can be processed and formed through a common photoetching process, electron beam exposure is not needed, processes such as high-precision cavity surface cleavage are not needed, multiple times of epitaxial growth is not needed, and the reflection efficiency is easy to design.

Semiconductor optical waveguide

In the present application, the semiconductor optical waveguide may include a first semiconductor optical waveguide and a second semiconductor optical waveguide. At least one of the first semiconductor optical waveguide and the second semiconductor optical waveguide is a gain optical waveguide, that is, at least one of the first semiconductor optical waveguide and the second semiconductor optical waveguide can provide loop gain for the corresponding optical resonant cavity. For example, if the first semiconductor optical waveguide is a gain optical waveguide, the first semiconductor optical waveguide may provide loop gain for the first optical resonator. For another example, if the second semiconductor optical waveguide is a gain waveguide, the second semiconductor optical waveguide can provide loop gain for the second optical resonator. For another example, the first semiconductor optical waveguide and the second semiconductor optical waveguide are both gain waveguides, and the first semiconductor optical waveguide may provide loop gain for the first optical resonant cavity, and the second semiconductor optical waveguide may provide loop gain for the second optical resonant cavity.

In one possible implementation, the first semiconductor optical waveguide and the second semiconductor optical waveguide may both be group III-V material optical waveguides.

Fig. 5 is a schematic structural diagram of another III-V material optical waveguide provided herein. The group III-V material optical waveguides may be first and second semiconductor optical waveguides. The optical waveguide of the III-V group material sequentially comprises a P-InGaAs layer/a P-InP cladding layer/an active layer/an N-InP layer from top to bottom. Further, the active layer may alternatively be composed of multiple quantum well materials such as III-VMQW or quantum dot materials such as III-VQD.

Three, optical resonant cavity

In the present application, the optical resonator includes a first optical resonator and a second optical resonator coupled to each other. Further alternatively, the optical coupling efficiency of the first optical resonant cavity and the second optical resonant cavity may be determined based on the reflectivity of the second reflective mirror surface. Wherein the optical coupling efficiency may be equal to the optical intensity in the first optical resonator into the second optical resonator/the total optical intensity in the first optical resonator; alternatively, the optical coupling efficiency is equal to the optical intensity in the second optical cavity into the first optical cavity/the total optical intensity in the second optical cavity. In this way, stable single-mode laser output of the laser can be achieved by optimizing the reflectivity of the second reflecting mirror surface, for example, in order to make the side mode suppression ratio of the output single-mode wavelength high, the coupling efficiency of the two cavities needs to be high, and the reflectivity of the second reflecting mirror surface needs to be small; in order to increase the output optical power, the second reflecting surface needs to have a high reflectance, and the second reflecting surface can be optimally designed by taking both of these characteristics into consideration.

Based on the possible structures of the first mirror surface, the second mirror surface, and the third mirror surface described above, three possible structures for forming two optical resonant cavities are exemplarily shown as follows.

In structure 1, the first mirror surface, the second mirror surface and the third mirror surface are Sagnac loop mirror surface waveguides.

That is, the first mirror facet is a first Sagnac loop mirrored waveguide, the second mirror facet is a second Sagnac loop mirrored waveguide, and the third mirror facet is a third Sagnac loop mirrored waveguide.

Fig. 6a is a schematic diagram illustrating a structure of two optical resonant cavities coupled to each other according to the present application. The two mutually coupled optical resonant cavities are respectively a first optical resonant cavity and a second optical resonant cavity, and the first optical resonant cavity is formed by a first semiconductor optical waveguide and a first Sagnac ring mirror surface waveguide and a second Sagnac ring mirror surface waveguide which are respectively positioned at two ends of the first semiconductor optical waveguide; the second optical resonator is formed of a second semiconductor optical waveguide and a second Sagnac loop mirror waveguide and a third Sagnac loop mirror waveguide respectively located at both ends of the second semiconductor optical waveguide. It should be noted that fig. 6a illustrates an example in which the cavity length of the second optical resonant cavity is longer than the long cavity length of the first optical resonant cavity.

Referring to fig. 6b, taking the first Sagnac loop mirror waveguide and the first semiconductor optical waveguide as an example, it is exemplarily shown that the decreasing direction of the width of the end of the first Sagnac loop mirror waveguide connected to the first semiconductor optical waveguide is opposite to the decreasing direction of the width of the end of the first semiconductor optical waveguide connected to the first Sagnac loop mirror waveguide. In the same manner, the direction of decrease in the width of the end of the second Sagnac loop mirror waveguide connected to the first semiconductor optical waveguide is opposite to the direction of decrease in the width of the end of the first semiconductor optical waveguide connected to the second Sagnac loop mirror waveguide; the direction of decrease in the width of the end of the second Sagnac loop-mirror waveguide connected to the second semiconductor optical waveguide is opposite to the direction of decrease in the width of the end of the second semiconductor optical waveguide connected to the second Sagnac loop-mirror waveguide; the direction of decrease in the width of the end of the third Sagnac loop-mirror waveguide connected to the second semiconductor optical waveguide is opposite to the direction of decrease in the width of the end of the second semiconductor optical waveguide connected to the third Sagnac loop-mirror waveguide. This contributes to improvement in the optical coupling efficiency between the semiconductor optical waveguide and the mirror surface.

For convenience of description, in the following description, an end of the first semiconductor optical waveguide connected to the first Sagnac loop mirror waveguide is referred to as a first end of the first semiconductor optical waveguide, and an end connected to the second Sagnac loop mirror waveguide is referred to as a second end of the first semiconductor optical waveguide; one end of the second semiconductor optical waveguide, which is connected with the second Sagnac loop mirror waveguide, is called a first end of the second semiconductor optical waveguide, and one end of the second semiconductor optical waveguide, which is connected with the third Sagnac loop mirror waveguide, is called a second end of the second semiconductor optical waveguide; one end of the first Sagnac loop-mirror waveguide connected to the first semiconductor optical waveguide is referred to as a first end of the first Sagnac loop-mirror waveguide; one end of the second Sagnac loop-mirror waveguide connected to the first semiconductor optical waveguide is referred to as a first end of the second Sagnac loop-mirror waveguide, and one end of the second Sagnac loop-mirror waveguide connected to the second semiconductor optical waveguide is referred to as a first end of the second Sagnac loop-mirror waveguide; the end of the third Sagnac loop-mirrored waveguide connected to the second semiconductor optical waveguide is referred to as the first end of the third Sagnac loop-mirrored waveguide.

That is, the decreasing directions of the widths of both ends to which the first semiconductor optical waveguide is connected respectively with the first Sagnac loop-mirror waveguide and the second Sagnac loop-mirror waveguide are opposite, and the decreasing directions of the widths of both ends to which the second semiconductor optical waveguide is connected respectively with the second Sagnac loop-mirror waveguide and the third Sagnac loop-mirror waveguide are opposite; the width of the first end of the first semiconductor optical waveguide, the width of the second end of the first semiconductor optical waveguide, the width of the first end of the second semiconductor optical waveguide, and the width of the second end of the second semiconductor optical waveguide may all be gradually reduced from 3um to 0.5 um. Further, alternatively, the reduction may be uniform (e.g., forming a trapezoid), or non-uniform, which is not limited in this application.

In one possible implementation, the width of the first end of the first Sagnac loop mirror waveguide, the width of the first end of the second Sagnac loop mirror waveguide, the width of the second end of the second Sagnac loop mirror waveguide, and the width of the first end of the third Sagnac loop mirror waveguide may each be tapered from 400nm to 100 nm. Further, alternatively, the reduction may be uniform (e.g., forming a trapezoid), or non-uniform, which is not limited in this application.

In one possible implementation, the width of the first end of the first semiconductor optical waveguide is greater than or equal to the width of the first end of the first Sagnac loop mirror waveguide; the width of the second end of the first semiconductor optical waveguide is greater than or equal to the width of the first end of the second Sagnac loop mirror waveguide; the width of the first end of the second semiconductor optical waveguide is greater than or equal to the width of the second end of the second Sagnac loop-mirror waveguide; the width of the first end of the second semiconductor optical waveguide is greater than or equal to the first end of the third Sagnac loop-mirror waveguide. Thus, the coupling efficiency of light in the two cavities can be ensured.

Further, optionally, the length of the first end of the first semiconductor optical waveguide, the length of the second end of the first semiconductor optical waveguide, the length of the first end of the second semiconductor optical waveguide, and the length of the second end of the second semiconductor optical waveguide are all greater than or equal to 10um and less than or equal to 200 um; the length of the first end of the first Sagnac loop mirror waveguide, the length of the first end of the second Sagnac loop mirror waveguide, the length of the second end of the second Sagnac loop mirror waveguide, and the length of the first end of the third Sagnac loop mirror waveguide are all greater than or equal to 10um and less than or equal to 200 um.

In one possible implementation, the optical coupling efficiency of the Sagnac loop-mirror waveguide and the semiconductor optical waveguide can be improved by controlling the length of the first end of the first Sagnac loop-mirror waveguide, the length of the first end and the length of the second end of the second Sagnac loop-mirror waveguide, the length of the first end and the length of the second end of the third Sagnac loop-mirror waveguide, and the length of the first end and the length of the second end of the second semiconductor optical waveguide.

As shown in fig. 6c, a graph showing the relationship between the optical coupling efficiency of a semiconductor optical waveguide and a Sagnac loop mirror waveguide and the length of one end of the semiconductor optical waveguide connected to the Sagnac loop mirror waveguide is provided. For convenience of explanation, a first end of the first semiconductor optical waveguide and a first end of the first Sagnac loop mirror waveguide are taken as an example. As can be seen from fig. 6c, when the length of the first end of the first semiconductor optical waveguide is less than 20um, the optical coupling efficiency increases with the increase of the length of the first end of the first semiconductor optical waveguide; when the length of the first end of the first semiconductor optical waveguide is equal to 20um, the optical coupling efficiency reaches substantially saturation, about 90%. When the length of the first end of the first semiconductor optical waveguide is greater than 20um, the optical coupling efficiency is substantially unchanged. It should be noted that, the relationship between the length of the first end of the second semiconductor optical waveguide and the optical coupling efficiency, and the relationship between the length of the second end of the second semiconductor optical waveguide and the optical coupling efficiency can be referred to the related description of fig. 6c, and the description thereof is not repeated here.

In order to realize high optical coupling efficiency and ensure that the length of the connection end of the semiconductor optical waveguide and the Sagnac ring mirror waveguide is short (contributing to miniaturization of the laser). In one possible implementation, the length of the first end of the first semiconductor optical waveguide is equal to the length of the first end of the first Sagnac-ring mirrored waveguide, and the length of the second end of the first semiconductor optical waveguide is equal to the length of the first end of the second Sagnac-ring mirrored waveguide; the length of the first end of the second semiconductor optical waveguide is equal to the length of the second end of the second Sagnac-ring mirrored waveguide and the length of the second end of the second semiconductor optical waveguide is equal to the length of the first end of the third Sagnac-ring mirrored waveguide.

In one possible implementation, the first semiconductor optical waveguide and the second semiconductor optical waveguide may be both group III-V material optical waveguides, and the first mirror surface, the second mirror surface, and the third mirror surface may be all silicon optical waveguides. Alternatively, the first semiconductor optical waveguide, the second semiconductor optical waveguide and the second reflecting mirror surface may all be III-V material optical waveguides, and the first reflecting mirror surface and the third reflecting mirror surface may all be silicon optical waveguides. Alternatively, the first semiconductor optical waveguide, the second semiconductor optical waveguide, the first mirror surface, the second mirror surface, and the third mirror surface may all be III-V material optical waveguides. That is, the laser may be a III-V/silicon hetero-integrated laser; alternatively, a group III-V homointegrated laser is also possible.

In one possible implementation, the heterogeneous integration of III-V material optical waveguides and silicon optical waveguides includes, but is not limited to, wafer-to-wafer bonding, and the like. Thus, the wafer-wafer bonding or the chip-wafer bonding can realize adiabatic coupling, and the adiabatic coupling helps to avoid changing the refractive index of the first semiconductor optical waveguide and/or the second semiconductor optical waveguide, thereby helping to avoid causing the cavity length of the first optical resonant cavity to change and/or the cavity length of the second optical resonant cavity to change, so that the cavity lengths of the two optical resonant cavities can be accurately controlled, and the laser can be helped to output stable single-mode laser.

In one possible implementation, the first end of the first semiconductor optical waveguide is farther from the substrate (closer to the upper surface) than the first end of the first Sagnac ring mirrored waveguide, i.e., the first Sagnac ring mirrored waveguide is closer to the substrate than the first end of the first semiconductor optical waveguide. That is, the substrate, the first end of the first Sagnac loop mirror waveguide, and the first end of the first semiconductor optical waveguide are included in this order from top to bottom. It is to be understood that the positional relationship between the second end of the first semiconductor optical waveguide and the first end of the second Sagnac ring mirrored waveguide, the positional relationship between the first end of the second semiconductor optical waveguide and the first end of the second Sagnac ring mirrored waveguide, and the positional relationship between the second end of the second semiconductor optical waveguide and the first end of the third Sagnac ring mirrored waveguide can be referred to as the positional relationship between the first end of the first semiconductor optical waveguide and the first end of the first Sagnac ring mirrored waveguide.

Referring to fig. 6d in conjunction with fig. 6a, a schematic diagram of the cavity length of an optical resonant cavity provided in the present application is shown. The cavity length of the first optical resonant cavity is equal to the sum of half the length of the first Sagnac loop mirror waveguide, half the length of the first semiconductor optical waveguide, and half the length of the second Sagnac loop mirror waveguide, and the cavity length of the second optical resonant cavity is equal to the sum of half the length of the second Sagnac loop mirror waveguide, half the length of the second semiconductor optical waveguide, and half the length of the third Sagnac loop mirror waveguide.

Because the Sagnac loop mirror waveguide can be manufactured by photoetching, the cavity length of the optical resonant cavity can be accurately controlled by designing the positions of the first reflecting mirror surface, the second reflecting mirror surface and the third reflecting mirror surface, generally, the cavity length error of the optical resonant cavity with the Sagnac loop mirror surface as the reflecting mirror surface is about +/-1 um and is far less than the cavity length error (more than +/-10 um) of the optical resonant cavity formed by forming the mirror surface according to the natural cleavage surface of a semiconductor wafer in the prior art, and therefore, when the first reflecting mirror surface is the Sagnac loop mirror waveguide, the cavity length error of the optical resonant cavity of the laser can be favorably reduced. That is, the cavity length of the first optical resonator and the cavity length of the second optical resonator can be defined by Sagnac toroidal mirror, and therefore, the cavity length of the first optical resonator and the cavity length of the second optical resonator can be accurately controlled, thereby contributing to the improvement of the stability of the output mode of the laser.

In the structure 2, the first reflector surface and the third reflector surface are both Sagnac ring mirror surface waveguides, and the second reflector surface is a deep etched groove waveguide.

That is, the first mirror facet is a first Sagnac loop-mirrored waveguide, the second mirror facet is a deep-etched trench waveguide, and the third mirror facet is a third Sagnac loop-mirrored waveguide.

Fig. 7a is a schematic diagram of another structure of two optical resonant cavities coupled with each other according to the present application. The two mutually coupled optical resonant cavities are respectively a first optical resonant cavity and a second optical resonant cavity, and the first optical resonant cavity is formed by a first semiconductor optical waveguide, a first Sagnac ring mirror surface waveguide and a deep etched groove waveguide which are respectively positioned at two ends of the first semiconductor optical waveguide; the second optical resonant cavity is formed by a second semiconductor optical waveguide, and a deep-etched trench waveguide and a third Sagnac loop mirror waveguide which are respectively positioned at two ends of the second semiconductor optical waveguide.

In one possible implementation, the decreasing direction of the width of the end of the first Sagnac loop mirror waveguide connected to the first semiconductor optical waveguide is opposite to the decreasing direction of the width of the end of the first semiconductor optical waveguide connected to the first Sagnac loop mirror waveguide; the direction of decrease in the width of the end of the third Sagnac loop-mirror waveguide connected to the second semiconductor optical waveguide is opposite to the direction of decrease in the width of the end of the second semiconductor optical waveguide connected to the third Sagnac loop-mirror waveguide. Reference is made here to the above description relating to fig. 6b, and no further description is repeated here.

In order to avoid as much as possible the influence on the power and lasing wavelength of the laser, the length of the deep-etched trench waveguide is an odd multiple of one quarter of the lasing wavelength. For example, the length of the trench waveguide etched back may be 10-100 um. The width is typically greater than the waveguide width of the laser, e.g., 1um to 30 um.

In conjunction with FIG. 5 above, the depth of the deep etched trench waveguide is less than or equal to the sum of the thicknesses of the P-InGaAs layer and the P-InP cladding layer. That is, the active layer cannot be etched when the first semiconductor optical waveguide or the second semiconductor optical waveguide is etched back. For example, the depth of the trench waveguide etched back can be 10-100 um. Since the active layer is used for emitting light, etching the active layer may affect the lifetime of light emitted from the active layer. That is, the deep etched trench waveguide is not etched to the active layer, which helps to prevent the deep etching from affecting the lifetime of the light emitted from the active layer.

Further, optionally, the length of the first end of the first semiconductor optical waveguide and the length of the second end of the second semiconductor optical waveguide are both greater than or equal to 10um and less than or equal to 200 um; the length of the first end of the first Sagnac loop-mirrored waveguide and the length of the first end of the third Sagnac loop-mirrored waveguide are both greater than or equal to 10um and less than or equal to 200 um.

It should be noted that the relationship between the optical coupling efficiency of the first end of the first semiconductor optical waveguide and the first end of the first Sagnac-ring mirror waveguide, and the optical coupling efficiency of the second end of the second semiconductor optical waveguide and the first end of the third Sagnac-ring mirror waveguide can be referred to the description of fig. 6c, and the description thereof is not repeated here. In addition, the width of the first end of the first semiconductor optical waveguide, the width of the second end of the second semiconductor optical waveguide, the width of the first end of the first Sagnac-ring mirror waveguide, and the width of the first end of the third Sagnac-ring mirror waveguide can be referred to the description of the related contents, and the detailed description thereof is omitted.

Referring to fig. 7b in conjunction with fig. 7a, there is provided a schematic diagram of the cavity length of another optical resonant cavity according to the present application. The cavity length of the first optical resonant cavity is equal to half of the length of the first Sagnac loop mirror waveguide, half of the length of the deep-etched trench waveguide, and the length of the first semiconductor optical waveguide, and the cavity length of the second optical resonant cavity is equal to half of the length of the deep-etched trench waveguide, half of the length of the third Sagnac loop mirror waveguide, and the length of the second semiconductor optical waveguide.

Because the Sagnac loop mirror waveguide is used as the first reflecting mirror and the third emitting mirror, the accuracy of controlling the cavity length of the optical resonant cavity is improved, and the stability of the output mode of the laser is improved. Further, since the second reflecting mirror is a trench waveguide formed by deep etching the first semiconductor optical waveguide or the second semiconductor optical waveguide, the length is small, thereby contributing to miniaturization of the laser.

Further, optionally, the deeply etched trench waveguide on the first semiconductor optical waveguide or the second semiconductor optical waveguide may also be used as an isolation region, so that different currents can be input into the first semiconductor optical waveguide and the second semiconductor optical waveguide, that is, electrical isolation is realized; but also light reflection can be realized.

And in the structure 3, the first reflector surface and the third reflector surface are both total-reflection MMI (microwave monolithic integrated circuit) reflective waveguides, and the second reflector surface is a deep-etched groove waveguide.

That is, the first reflector is the first total-reflection MMI reflection waveguide, the second reflector is the deep-etched trench waveguide, and the third reflector is the third total-reflection MMI reflection waveguide.

Fig. 8a is a schematic diagram of a structure of two optical resonant cavities coupled with each other according to the present application. The two mutually coupled optical resonant cavities are respectively a first optical resonant cavity and a second optical resonant cavity, and the first optical resonant cavity is formed by a first semiconductor optical waveguide, a first total-reflection MMI reflection waveguide and a deep-etched groove waveguide which are respectively positioned at two ends of the first semiconductor optical waveguide; the second optical resonant cavity is formed by a second semiconductor optical waveguide, a deep-etched groove waveguide and a third total-reflection MMI reflection waveguide which are respectively positioned at two ends of the second semiconductor optical waveguide.

In a possible implementation manner, one end of the first total-reflection MMI reflection waveguide is connected to one end of the first semiconductor optical waveguide, and the other end of the first total-reflection MMI reflection waveguide is two end faces perpendicular to each other, and is used for performing total reflection on light. Further, optionally, the first fully reflective MMI reflective waveguide may further comprise an output waveguide operable to output a portion of the light in the first fully reflective MMI reflective waveguide.

In a possible implementation manner, one end of the third total-reflection MMI reflection waveguide is connected with one end of the second semiconductor optical waveguide, and the other end of the third total-reflection MMI reflection waveguide is two end faces perpendicular to each other, and is used for performing total reflection on light.

Referring to fig. 8b in conjunction with fig. 8a, a schematic diagram of a cavity length of another optical resonant cavity provided in the present application is shown. The cavity length of the first optical resonant cavity is equal to the length of the first fully-reflected MMI reflection waveguide, the length of the deeply-etched groove waveguide and the length of the first semiconductor optical waveguide, and the cavity length of the second optical resonant cavity is equal to the length of the deeply-etched groove waveguide, the length of the third fully-reflected MMI reflection waveguide and the length of the second semiconductor optical waveguide.

Further, optionally, an isolation region formed by etching may be further included between the first semiconductor optical waveguide and the second semiconductor optical waveguide, and by providing the isolation region, different currents may be input to the first semiconductor optical waveguide and the second semiconductor optical waveguide, that is, electrical isolation may be achieved; and the isolation region can also realize light reflection.

It should be noted that possible structures for forming the two optical resonant cavities may also be other structures, for example, the first mirror surface and the second mirror surface are Sagnac loop mirror surface waveguides, and the third mirror surface is a total reflection MMI reflection waveguide, which is not described in detail herein.

The gain region of the laser produces light that can be lased only if sufficient reflection is obtained at both optical cavities at the same time. That is, lasing occurs when the resonant wavelengths of the two optical cavities coincide and only one coincides. In the present application, the first semiconductor optical waveguide may be formed by changing a first current injected into the first semiconductor optical waveguide or changing a temperature of the first semiconductor optical waveguide; and/or by varying a second current injected into the second semiconductor optical waveguide or varying a temperature of the second semiconductor optical waveguide; the resonance wavelength of the first optical resonant cavity and the resonance wavelength of the second optical resonant cavity are overlapped in the respective gain spectrum range, and only one wavelength is overlapped, so that the laser outputs single-mode wavelength.

The resonant frequency interval of the first optical resonant cavity is Δ f₁The frequency interval of the second optical resonant cavity is Deltaf₂For illustration purposes. Frequency interval deltaf of the second optical resonator₂The frequency separation Δ f from the first optical resonator is required₁There is a certain difference between them, so that there is only one resonance peak exactly coinciding with the first optical resonator and the second optical resonator within the gain window (or called gain spectrum) of the gain waveguide.

Wherein C is the speed of light in vacuum, L₁Is the cavity length of the first optical resonator, n_g1Is the effective group refractive index, L, of the first semiconductor optical waveguide₂Is the cavity length, n, of the second optical resonator_g2Is the effective group index of the second semiconductor optical waveguide.

By varying the effective refractive index n_g1Can change Δ f₁Thereby influencing the frequency tuning of the first optical resonator by changing the effective refractive index n_g2Can change Δ f₂Thereby affecting the frequency tuning of the second optical resonator. That is, the resonant frequency interval Δ f of the first optical resonator₁And the resonant frequency interval of the second optical resonant cavity₂In contrast, it is possible for only one resonance frequency of the first optical resonator and the second optical resonator to coincide in the gain spectrum range.

When the frequency spectrum of the first optical resonant cavity is superposed with the frequency spectrum of the second optical resonant cavity, the interval between adjacent superposed resonance peaks can be obtained as deltaf.

The working frequency of the whole laser is determined by the frequency of the coincident resonant peak of the first optical resonant cavity and the second optical resonant cavity, and the first optical resonant cavity and/or the second optical resonant cavity are/is tuned to cause the working frequency of the laser to move by deltaf₁Δf₂The variation of the operating frequency of the laser can be considered to have an amplification factor δ f, and the amplification effect of the variation is called Vernier caliper (Vernier) effect.

Based on whether the first semiconductor optical waveguide and the second semiconductor optical wave are gain waveguides, three possible cases are given below exemplarily, which are all exemplified by the above structure 1, and it is understood that the following three cases are also applicable to the above structures 2 and 3. For example, if a current is injected into the first semiconductor optical waveguide and a gain is generated, the first semiconductor optical waveguide is a gain waveguide; for another example, if a current is injected into the second semiconductor optical waveguide and a gain is generated, the second semiconductor optical waveguide is a gain waveguide.

In case 1, the first semiconductor optical waveguide and the second semiconductor optical waveguide are both gain waveguides.

In conjunction with fig. 6a described above, the laser may further comprise a first electrode and a second electrode, as can be seen in fig. 9a, the first electrode may be disposed on the first semiconductor optical waveguide and the second electrode may be disposed on the second semiconductor optical waveguide. The first electrode is used for injecting a first current into the first semiconductor optical waveguide; the second electrode is used for injecting a second current into the second semiconductor optical waveguide, wherein the first current is larger than the current threshold of the first optical resonant cavity, and the second current is larger than the current threshold of the second optical resonant cavity. Therefore, the resonance wavelength of the first optical resonant cavity and the resonance wavelength of the second optical resonant cavity are overlapped in the respective gain spectrum range and only one wavelength is overlapped, and the laser can output single-mode laser.

Fig. 9b is a schematic structural diagram of another laser provided by the present application, which is shown in fig. 8a in combination with fig. 8 a. The laser may further include a first electrode and a second electrode, the first electrode may be disposed on the first semiconductor optical waveguide, and the second electrode may be disposed on the second semiconductor optical waveguide. For the related description of the first electrode and the second electrode, reference may be made to the description of fig. 9a, and the description is not repeated here. In conjunction with fig. 5 above, the first and second electrodes may share an N-InP layer, as can be seen in the structure of fig. 9 c. It should be noted that, the deeply etched trench waveguide is located between the first electrode and the second electrode, and it can be realized that the current between the first semiconductor optical waveguide and the second semiconductor optical waveguide has no influence.

Based on this case 1, it is possible to make the resonance wavelength of the first optical resonance cavity and the resonance wavelength of the second optical resonance cavity coincide with each other by only one wavelength in the respective gain spectrum ranges by two implementations exemplarily shown below.

The first implementation mode is electric tuning.

Based on the laser shown above, as shown in fig. 10, a schematic diagram of the laser output of a laser is exemplarily shown for the present application. When the first electrode injects a first current into the first semiconductor optical waveguide, the first semiconductor optical waveguide can output a wavelength as shown in (a) of fig. 10; when the second electrode inputs the second current to the second semiconductor optical waveguide, the second semiconductor optical waveguide may be made to output a wavelength as shown in (b) of fig. 10, and the wavelength output by the first semiconductor optical waveguide and the wavelength output by the second semiconductor optical waveguide may overlap by one and only one wavelength in a gain spectrum (as shown in (c) of fig. 10), that is, the wavelength of the laser light output by the laser device is shown in (d) of fig. 10.

In the application, the relative optical path difference between the first optical resonant cavity and the second optical resonant cavity can be changed by changing the first current and/or the second current, so that the coincident wavelength of the resonance wavelength of the first optical resonant cavity and the resonance wavelength of the second optical resonant cavity can be changed, the wavelength of laser output by the laser can be changed, and the wavelength tuning of the laser is realized.

Based on the first implementation manner, the tunable wavelength range of the laser is Δ λ 1.

Wherein L is₁Denotes the cavity length, L, of the first optical resonator₂Denotes the cavity length, n, of the second optical resonator_gThe group refractive index of the connecting portion between the semiconductor optical waveguide and the mirror surface is shown.

Implementation two, thermal tuning.

In one possible implementation, the laser may further include a first thin film resistor and a second thin film resistor, and referring to fig. 11, the laser may include a first optical resonant cavity, a second optical resonant cavity, a first electrode and/or a second electrode (fig. 11 exemplifies the inclusion of the first electrode and the second electrode), the first thin film resistor and the second thin film resistor formed, the first electrode may be disposed on the first semiconductor optical waveguide, and the second electrode may be disposed on the second semiconductor optical waveguide. The first electrode is used for injecting a first current into the first semiconductor optical waveguide, and the second electrode is used for injecting a second current into the second semiconductor optical waveguide; the first thin film resistor is disposed adjacent to the first semiconductor optical waveguide, and the second thin film resistor is disposed adjacent to the second semiconductor optical waveguide. A third electrode and a fourth electrode are respectively arranged at two ends of the first thin film resistor, and a fifth electrode and a sixth electrode are respectively arranged at two ends of the second thin film resistor; the third electrode and the fourth electrode are used for injecting a third current into the first thin film resistor, and the third current is used for carrying out thermal regulation on the first thin film resistor; the fifth electrode and the sixth electrode are used for injecting a fourth current into the second thin-film resistor, and the fourth current is used for thermally adjusting the second thin-film resistor, so that the resonant wavelength of the first optical resonant cavity and the resonant wavelength of the second optical resonant cavity are overlapped in a gain spectrum and only one wavelength is overlapped, and the laser outputs single-mode laser.

In the present application, the heat of the first thin film resistor can be changed by changing the third current, thereby changing the refractive index of the first semiconductor optical waveguide; and/or, by changing the fourth current, the heat of the second thin film resistor is changed, thereby changing the refractive index of the second semiconductor optical waveguide; furthermore, the relative optical path difference between the first optical resonant cavity and the second optical resonant cavity can be changed, so that the coincident wavelength of the resonance wavelength of the first optical resonant cavity and the resonance wavelength of the second optical resonant cavity is changed, the wavelength of the laser output by the laser can be changed, and the wavelength tuning of the laser is realized.

Based on the second implementation manner, the principle of the laser output by the laser device can be described with reference to fig. 10, and the description thereof is not repeated.

It should be noted that the laser shown in fig. 11 may include at least one of the first electrode and the second electrode. If the laser includes a first electrode, the first current is greater than a current threshold of the first optical resonator; if the laser includes a second electrode, the second current is greater than a current threshold of the second optical resonator; if the laser includes a first electrode and a second electrode, the first current is greater than a current threshold of the first optical resonator and the second current is greater than a current threshold of the second optical resonator.

In case 2, the first semiconductor optical waveguide is a gain waveguide, and the second semiconductor optical waveguide is a filter.

In a possible implementation manner, the laser may further include a first electrode, a second thin film resistor, a fifth electrode, and a sixth electrode, and referring to fig. 12, the first electrode may be disposed on the first semiconductor optical waveguide, the second thin film resistor is disposed beside the second semiconductor optical waveguide, and the fifth electrode and the sixth electrode are disposed at two ends of the second thin film resistor, respectively. The first electrode is used for injecting a first current into the first semiconductor optical waveguide, wherein the first current is larger than a current threshold value of the first optical resonant cavity; the fifth electrode and the sixth electrode are used for injecting a fourth current into the second thin film resistor, and the fourth current is used for carrying out thermal regulation on the second thin film resistor. In this way, the filter allows only one and only one of the resonant wavelengths of the first optical resonant cavity to pass, so that the laser can output single-mode laser light.

Fig. 13 is a schematic diagram of another laser output device exemplarily shown in the present application. When the first electrode outputs the first current to the first semiconductor optical waveguide, the output wavelength of the first semiconductor optical waveguide is as shown in (a) of fig. 13; when the fifth electrode and the sixth electrode are used to inject the fourth current into the second thin-film resistor, the second semiconductor optical waveguide may output light of a specific wavelength, which may be one of the output wavelengths of the first semiconductor optical waveguide, as shown in fig. 13 (b).

Based on this case 2, it is possible to make the resonance wavelength of the first optical resonance cavity and the resonance wavelength of the second optical resonance cavity coincide with each other by only one wavelength in the respective gain spectrum ranges by two implementations exemplarily shown below.

Implementation 1, thermal tuning.

The wavelength allowed to be output by the second optical resonator can be changed by changing the refractive index of the second semiconductor optical waveguide by changing the magnitude of the fourth current while maintaining the magnitude of the first current unchanged, so that the laser can output single-mode laser light with different wavelengths, as shown in (d) in fig. 13, that is, wavelength tuning of the laser is realized. That is, wavelengths that are not of interest can be filtered out by filters that can be used to select one or more discrete wavelengths to pass through so that stimulated emission of those wavelengths is suppressed. The filter is a tunable filter, or may be referred to as a wavelength selector.

Based on this case 2, the tunable wavelength range of the laser is Δ λ 2.

Where n denotes an effective refractive index of the second semiconductor optical waveguide, Δ n denotes a change in the effective refractive index corresponding to the second semiconductor optical waveguide, and the effective refractive index of the second semiconductor optical waveguide is different depending on the magnitude of the fourth current.

When the second semiconductor optical waveguide is used as a filter, the width of the Free Spectral Range (FSR) of the filter is greater than or equal to the width of the gain spectrum of the first semiconductor optical waveguide, and may be greater than 50nm, for example. In this way it can be achieved that the filter has only one wavelength in the gain spectrum range of the first semiconductor optical waveguide.

Implementation 2, electrical tuning.

Referring to the structure shown in fig. 9a or 9b, the first electrode is used to inject a first current into the first semiconductor optical waveguide, and the second electrode is used to inject a fifth current into the second semiconductor optical waveguide, where the first current is greater than a current threshold of the first optical resonant cavity, so that the magnitude of the first current is maintained, and the fifth current is changed, so that the filter can allow light with different wavelengths to pass through, and thus the laser can output single-mode laser with different wavelengths, that is, wavelength tuning of the laser is achieved. It will be appreciated that the fifth current is less than the current threshold of the second optical resonator and the bandgap wavelength of the core layer of the second semiconductor optical waveguide is less than the bandgap wavelength of the core layer of the first semiconductor optical waveguide, that is, the first semiconductor optical waveguide is an active region and the second semiconductor optical waveguide is a passive region.

In case 3, the first semiconductor optical waveguide is a filter, and the second semiconductor optical waveguide is a gain waveguide.

In a possible implementation manner, the laser may further include a second electrode, a first thin film resistor, a third electrode, and a fourth electrode, referring to fig. 14, the second electrode may be disposed on the second semiconductor optical waveguide, the first thin film resistor is disposed beside the first semiconductor optical waveguide, and the third electrode and the fourth electrode are disposed at two ends of the first thin film resistor, respectively. The second electrode is used for injecting a second current into the second semiconductor optical waveguide, and the second current is larger than the current threshold value of the second optical resonant cavity; the third electrode and the fourth electrode are used for injecting a third current into the first thin film resistor, and the third current is used for carrying out thermal regulation on the first thin film resistor. In this way, the filter allows only one and only one of the resonant wavelengths of the second optical resonant cavity to pass, so that the laser can output single-mode laser light.

Fig. 15 is a schematic diagram of the laser output of another laser exemplarily shown in the present application. When the second electrode outputs the second current to the second semiconductor optical waveguide, the gain spectrum of the second semiconductor optical waveguide is as shown in (a) of fig. 15; the first semiconductor optical waveguide can output light of a specified wavelength, which may be one of the wavelengths in the gain spectrum of the second semiconductor optical waveguide, as shown in fig. 15 (b). Therefore, by changing the magnitude of the third current, the wavelength of the output of the first semiconductor optical waveguide can be changed, so that the laser can be made to output single-mode laser light, as shown in (d) of fig. 15.

In this way, the tunable wavelength range of the laser is Δ λ 2.

Where n denotes an effective refractive index of the first semiconductor optical waveguide, Δ n denotes a change in the effective refractive index of the first semiconductor optical waveguide, and the magnitude of the third current is different and the effective refractive index of the first semiconductor optical waveguide is also different.

When the first semiconductor optical waveguide is used as a filter, the width of the Free Spectral Range (FSR) of the filter is greater than or equal to the width of the gain spectrum of the second semiconductor optical waveguide, and may be greater than 50nm, for example. In this way, a gain spectrum can be achieved in which the filter has only one wavelength in the second semiconductor optical waveguide.

Based on this case 3, the resonance wavelength of the first optical resonance cavity and the resonance wavelength of the second optical resonance cavity can be made to coincide with only one wavelength in the respective gain spectrum ranges by two implementations exemplarily shown below.

Implementation a, thermal tuning.

The third current can be changed to change the refractive index of the second semiconductor optical waveguide while keeping the magnitude of the second current unchanged, so that the filter can allow light with different wavelengths to pass through, and the laser can output single-mode laser light with different wavelengths, namely wavelength tuning of the laser is realized.

Implementation B, electrical tuning.

Referring to the structure shown in fig. 9a or 9b, the first electrode is configured to inject a sixth current into the first semiconductor optical waveguide, and the second electrode is configured to inject a second current into the second semiconductor optical waveguide, where the second current is greater than a current threshold of the second optical resonant cavity, so that the magnitude of the second current is maintained, and the sixth current is changed, so that the filter can allow light with different wavelengths to pass through, and thus the laser can output single-mode laser with different wavelengths, that is, wavelength tuning of the laser is achieved.

Based on this implementation B, the principle of outputting laser light by the laser device can be referred to the description of fig. 15, and the description is not repeated here.

In the embodiments of the present application, unless otherwise specified or conflicting with respect to logic, the terms and/or descriptions in different embodiments have consistency and may be mutually cited, and technical features in different embodiments may be combined to form a new embodiment according to their inherent logic relationship.

In the present application, "at least one" means one or more, "a plurality" means two or more. "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone, wherein A and B can be singular or plural. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single item(s) or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", wherein a, b, c may be single or plural. In the description of the text of this application, the character "/" generally indicates that the former and latter associated objects are in an "or" relationship. In the formula of the present application, the character "/" indicates that the preceding and following related objects are in a relationship of "division".

It is to be understood that the various numerical designations referred to in this application are merely for ease of description and are not intended to limit the scope of the embodiments of the present application. The sequence numbers of the above-mentioned processes do not mean the execution sequence, and the execution sequence of the processes should be determined by their functions and inherent logic. The terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. Furthermore, the terms "comprises" and "comprising," as well as any variations thereof, are intended to cover a non-exclusive inclusion, such as a list of steps or elements. A method, system, article, or apparatus is not necessarily limited to those steps or elements explicitly listed, but may include other steps or elements not explicitly listed or inherent to such process, system, article, or apparatus.

Although the present application has been described in conjunction with specific features and embodiments thereof, it will be evident that various modifications and combinations can be made thereto without departing from the spirit and scope of the application. Accordingly, the specification and figures are merely illustrative of the concepts defined by the appended claims and are intended to cover any and all modifications, variations, combinations, or equivalents within the scope of the application.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the embodiments of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to encompass such modifications and variations.