Coupled cavity semiconductor laser

Abstract

The invention provides a coupled cavity semiconductor laser, and relates to the technical field of optical fiber communication and semiconductor lasers. The coupled cavity semiconductor laser comprises an echo wall microcavity used for outputting an echo wall fundamental mode; the first end of the Fabry-Perot cavity is connected with the echo wall microcavity. The second end of the Fabry-Perot cavity is connected with the echo wall microcavity. Wherein the resonant mode of the Fabry-Perot cavity is coupled with the fundamental mode of the echo wall, and a light beam of the coupled mode is output from the second end of the Fabry-Perot cavity.

Description

Technical Field

[0001] The present disclosure relates to the technical fields of optical fiber communication and semiconductor lasers, and more particularly, to coupled cavity semiconductor lasers. Background Art

[0002] Semiconductor lasers are important components of fiber-optic communication systems and on-chip photonic integrated chips, and are inevitably affected by light feedback from other components or end faces in the system. Lasers are sensitive to external light feedback. When the feedback intensity is high, single-mode lasers will enter a coherent collapse state from a single-mode output state, and then increase intensity noise, widen line width, and mode hopping. This is particularly harmful to communication systems and will lead to problems such as increased bit error rates and crosstalk in pulse sequences. Summary of the invention

[0003] In view of this, the present disclosure provides a coupled cavity semiconductor laser, comprising: a whispering gallery microcavity for outputting a whispering gallery fundamental mode; and a Fabry-Perot cavity, wherein a first end of the Fabry-Perot cavity is connected to the whispering gallery microcavity; wherein a resonant mode of the Fabry-Perot cavity is coupled to the whispering gallery fundamental mode, and a light beam of a coupled mode is output from a second end of the Fabry-Perot cavity.

[0004] According to an embodiment of the present disclosure, a light beam is transmitted to a Fabry-Perot cavity along a whispering gallery microcavity, and the cross section of the whispering gallery microcavity is a hexagonal structure, a set of parallel opposite sides in the hexagonal structure is parallel to the first diagonal line in the hexagonal structure, and the length m of the set of parallel opposite sides is:

[0005] ,

[0006] Wherein, n is the length of the first diagonal line, and the first diagonal line is parallel to the direction in which the light beam is transmitted in the Fabry-Perot cavity.

[0007] According to an embodiment of the present disclosure, the whispering gallery microcavity includes: a rectangular hole disposed on the whispering gallery microcavity for suppressing high-order modes of the whispering gallery microcavity.

[0008] According to an embodiment of the present disclosure, a set of opposite sides of the rectangular hole is perpendicular to the direction in which the light beam is transmitted in the Fabry-Perot cavity, and the distance p between one side of the set of opposite sides away from the Fabry-Perot cavity and the straight line passing through the center point of the hexagonal structure is: , wherein the straight line is perpendicular to the first diagonal line.

[0009] According to an embodiment of the present disclosure, the length v of a set of opposite sides of the rectangular hole is: ; The length w of the other set of opposite sides of the rectangular hole is: , where d is the width of the Fabry-Perot cavity.

[0010] According to an embodiment of the present disclosure, the whispering gallery microcavity includes an N-type confinement layer, an active layer, and a P-type confinement layer stacked in sequence: wherein the light beam is transmitted from the whispering gallery microcavity to the Fabry-Perot cavity along a direction parallel to the stacked N-type confinement layer, the active layer, and the P-type confinement layer. According to an embodiment of the present disclosure, it also includes: an N-type substrate, which is disposed on a surface of the N-type confinement layer away from the active layer; an N-face electrode, which is disposed on a surface of the N-type substrate away from the N-type confinement layer; and an ohmic contact layer, which is disposed on a surface of the whispering gallery microcavity away from the N-type substrate and a surface of the Fabry-Perot cavity away from the N-type substrate, wherein an isolation groove is provided between the ohmic contact layers on the whispering gallery microcavity and the Fabry-Perot cavity; and a P-face electrode, which is disposed on the ohmic contact layer.

[0011] According to an embodiment of the present disclosure, the shape of the P-side electrode includes a polygon, an arc-edge polygon, a ring, or a circle.

[0012] According to an embodiment of the present disclosure, the internal material of the rectangular hole is benzocyclobutene; benzocyclobutene is provided around the whispering gallery microcavity that does not contain the P-side electrode and around the Fabry-Perot cavity that does not contain the P-side electrode, wherein the refractive index of benzocyclobutene is smaller than the refractive index of the whispering gallery microcavity and the Fabry-Perot cavity material.

[0013] A test system for a coupled cavity semiconductor laser, comprising: a DC bias; a laser, a first end of the laser connected to the DC bias; a circulator, a first end of the circulator connected to a second end of the laser; a first beam splitter, a first end of the first beam splitter connected to a second end of the circulator; a polarization controller, a first end of the polarization controller connected to a third end of the circulator; an optical attenuator, a first end of the optical attenuator connected to a second end of the first beam splitter; a second beam splitter, a first end of the second beam splitter connected to a second end of the optical attenuator, and a second end of the second beam splitter connected to a second end of the polarization controller. connection; a power meter, the power meter is connected to the third end of the second spectrometer; a third spectrometer, the first end of the third spectrometer is connected to the third end of the first spectrometer; a spectrometer, the spectrometer is connected to the second end of the third spectrometer; a photodetector, the first end of the photodetector is connected to the third end of the third spectrometer; a DC bias device, the first end of the DC bias device is connected to the second end of the photodetector; an electric amplifier, the first end of the electric amplifier is connected to the second end of the DC bias device; a spectrum analyzer, the spectrum analyzer is connected to the second end of the electric amplifier; and a multimeter, the multimeter is connected to the third end of the DC bias device.

[0014] According to the embodiments of the present disclosure, the whispering gallery fundamental mode with a high quality factor output by the whispering gallery microcavity is coupled with the resonant mode of the Fabry-Perot cavity, which greatly improves the anti-feedback capability and comprehensive output performance of the laser.

[0015] According to the embodiments of the present disclosure, the light beam is designed to be transmitted along the whispering gallery microcavity to the Fabry-Perot cavity. The cross-section of the whispering gallery microcavity is a hexagonal structure. The reflection spectrum envelope of the disordered mode in the microcavity when the cross-section is a square can be simplified, so that there is only a fundamental mode and a group of high-order mode envelopes between two groups of adjacent longitudinal modes of the microcavity, which has a relatively high mode reflectivity and makes the mode in the microcavity purer.

[0016] According to the embodiments of the present disclosure, by designing rectangular holes and thereby destroying the light field distribution of the high-order modes, the reflectivity of the high-order modes can be sufficiently lowered without changing the reflectivity of the fundamental mode. This allows the fundamental mode of the whispering gallery microcavity to have an absolute advantage in mode competition within a free spectrum range, and can then interact with the resonant mode in the Fabry-Perot cavity to form a coupled mode, allowing the microcavity laser to achieve stable single-mode lasing and have excellent static and dynamic characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0018] Figure 1 A schematic diagram of the three-dimensional structure of a coupled cavity semiconductor laser according to an embodiment of the present disclosure is shown;

[0019] Figure 2 Schematically shows a top view of a coupled cavity semiconductor laser according to an embodiment of the present disclosure;

[0020] Figure 3 A diagram schematically showing a mode field distribution diagram of a fundamental mode in a whispering gallery microcavity of a coupled cavity semiconductor laser according to an embodiment of the present disclosure;

[0021] Figure 4 A schematic diagram showing a mode field distribution diagram of a high-order mode in a whispering gallery microcavity of a coupled-cavity semiconductor laser according to an embodiment of the present disclosure;

[0022] Figure 5 Schematic diagram of the first diagonal n=18 of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present invention Schematic diagram of the variation of microcavity mode reflectivity with wavelength at μm;

[0023] Figure 6 Schematic diagram of the first diagonal n=18 of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present invention Schematic diagram of the variation of the quality factor of the coupled mode with wavelength at μm;

[0024] Figure 7Schematic diagram of the first diagonal n=16 of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present disclosure μm, the length of the FP cavity is L = 500 μm, and the injection current in the whispering gallery is I WGM =30mA, FP cavity injection current I FP =Spectrum diagram when 50mA;

[0025] Figure 8 Schematic diagram of the first diagonal n=16 of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present disclosure μm, the length of the FP cavity is L = 400 μm, and the injection current in the whispering gallery is I WGM =30mA, FP cavity injection current I FP =Spectrum diagram when 50mA;

[0026] Fig. 9 The PIV curve diagram of the coupled cavity semiconductor laser when the length of the FP cavity L=400 μm according to the embodiment of the present disclosure is schematically shown;

[0027] Fig.10 The anti-feedback testing system according to an embodiment of the present disclosure is schematically shown;

[0028] Fig.11 Schematic diagram of the first diagonal n=16 of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present disclosure μm, the length of the FP cavity is L = 500 μm, and the injection current in the whispering gallery is I WGM =30mA, FP cavity injection current I FP =Schematic diagram of the output spectrum changing with feedback intensity when 50mA;

[0029] Fig.12 Schematic diagram of the first diagonal n=16 of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present disclosure μm, the length of the FP cavity is L = 400 μm, and the injection current in the whispering gallery is I WGM =30mA, FP cavity injection current I FP =Schematic diagram of the output spectrum changing with feedback intensity when 50mA;

[0030] Fig.13 Schematic diagram of the first diagonal n=18 of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present disclosure μm, the length of the FP cavity is L = 400 μm, and the injection current in the whispering gallery is I WGM =30mA, FP cavity injection current I FP =Schematic diagram of the output spectrum changing with feedback intensity when 50mA;

[0031] Description of reference numerals:

[0032] 1: Whispering gallery microcavity; 2: FP cavity; 3: rectangular hole; 4: N-side electrode; 5: N-type substrate; 6: N-type confinement layer; 7: active layer; 8: P-type confinement layer; 9: Ohmic contact layer; 10: P-side electrode. DETAILED DESCRIPTION

[0033] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0034] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0035] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0036] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0037] Currently, the most common method to avoid the influence of optical feedback on lasers is to introduce isolators. For the field of optical fiber communications, this will increase the size of the device, reduce the output power, increase the difficulty of packaging, and greatly increase the cost of the system. For the field of photonic integration, there is still no suitable integrated isolator that can provide strong isolation and negligible insertion loss at the same time. Therefore, improving the intrinsic anti-feedback capability of lasers is a hot topic of current research.

[0038] Relevant studies have shown that the coherent collapse threshold of semiconductor lasers is inversely proportional to the fourth power of the effective linewidth enhancement factor, so using materials with lower effective linewidth enhancement factors or rationally designing the laser structure can effectively improve the anti-feedback capability of the laser. Compared with quantum well lasers, quantum dot lasers have better anti-feedback performance, but due to their higher difficulty in preparation, their comprehensive performance is still slightly inferior to that of quantum well lasers. Relevant theoretical and experimental studies have shown that the anti-feedback capability of the laser can be effectively improved by improving the quality factor (Q value) of the laser lasing mode, but the structure of traditional quantum well lasers often makes it difficult to effectively improve their mode Q value.

[0039] Since coupled cavity lasers have high-Q whispering gallery mode microcavities, the feedback light is not likely to affect the original lasing coupling mode, which makes coupled cavity lasers attract much attention in the field of anti-feedback research.

[0040] The lasing mode of common coupled cavity lasers is often a coupled mode formed by the coupling of the microcavity high-order whispering gallery mode and the resonant mode of the Fabry-Perot cavity (FP cavity for short). This is because the reflection peak of the high-order mode is wider and it is easier to form a good mode match with the resonant mode of the FP cavity. However, compared with the coupled mode formed by the whispering gallery fundamental mode, the coupled mode formed by the high-order mode has a lower Q value, which has limited improvement on the anti-feedback capability of the laser.

[0041] At the same time, the microcavity modes in existing square or diamond coupled cavity lasers are extremely complex. The fundamental mode with high Q value in the laser has no advantage in the mode competition of the microcavity, so the actual lasing is often the high-order coupled mode with low Q value, which makes it impossible to further improve the anti-feedback ability of the coupled cavity laser.

[0042] Based on this, the present invention outputs a whispering gallery fundamental mode with a high quality factor through the whispering gallery microcavity, which is coupled with the resonant mode of the FP cavity, and then outputs a coupled mode with a high Q value, which greatly improves the anti-feedback capability and comprehensive output performance of the laser.

[0043] Figure 1 The three-dimensional structure diagram of the coupled cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown.

[0044] Figure 2 A top view of a coupled cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown.

[0045] like Figure 1 and Figure 2As shown, the coupled cavity semiconductor laser provided in this embodiment may include: a whispering gallery microcavity 1, which is used to output a whispering gallery fundamental mode; a Fabry-Perot cavity 2, wherein the first end of the Fabry-Perot cavity is connected to the whispering gallery microcavity; wherein the resonant mode of the Fabry-Perot cavity is coupled with the whispering gallery fundamental mode, and a coupled mode light beam is output from the second end of the Fabry-Perot cavity.

[0046] In the embodiment of the present disclosure, an external light beam enters the whispering gallery microcavity after being incident from the second end of the FP cavity, and is reflected multiple times in the whispering gallery microcavity before being emitted from the second end face of the FP cavity. This embodiment outputs a whispering gallery fundamental mode with a high quality factor through the whispering gallery microcavity to couple with the resonant mode of the FP cavity, and then outputs a coupled mode with a high Q value, which greatly improves the anti-feedback capability and comprehensive output performance of the laser.

[0047] According to an embodiment of the present disclosure, a light beam is transmitted to a Fabry-Perot cavity along a whispering gallery microcavity, and the cross section of the whispering gallery microcavity is a hexagonal structure, a set of parallel opposite sides in the hexagonal structure is parallel to the first diagonal line in the hexagonal structure, and the length m of the set of parallel opposite sides is:

[0048] ,

[0049] Wherein, n is the length of the first diagonal line, and the first diagonal line is parallel to the direction in which the light beam is transmitted in the Fabry-Perot cavity.

[0050] In the embodiments of the present disclosure, the hexagonal structure is a shape in which a set of relative vertices are cut off from a square. When the light beam is transmitted along the whispering gallery microcavity to the Fabry-Perot cavity, the cross-section of the whispering gallery microcavity is controlled to be a hexagonal structure, so that the microcavity reflection spectrum envelope can be made simpler. Within a free spectrum range, there is only one set of fundamental modes and one set of high-order mode envelopes with relatively high mode reflectivity, which makes the mode in the microcavity purer.

[0051] Figure 3 The mode field distribution diagram of the fundamental mode in the whispering gallery microcavity of the coupled-cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown.

[0052] Figure 4 The mode field distribution diagram of the high-order mode in the whispering gallery microcavity of the coupled-cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown.

[0053] According to an embodiment of the present disclosure, the whispering gallery microcavity includes: a rectangular hole 3, which is arranged on the whispering gallery microcavity and is used to suppress the high-order modes of the whispering gallery microcavity.

[0054] In the embodiments of the present disclosure, Figure 3 and Figure 4As shown in the figure, the distribution of the high-order modes of the whispering gallery microcavity in the mode field is more concentrated in the center of the microcavity, while the mode field center distribution of the fundamental mode of the microcavity is weaker. Therefore, by setting rectangular holes at positions with higher high-order mode distribution intensity, it is possible to effectively suppress high-order modes while almost not affecting the reflectivity and Q value of the fundamental mode, so that the high-Q value fundamental mode can achieve stable single-mode emission.

[0055] According to an embodiment of the present disclosure, a set of opposite sides of the rectangular hole are perpendicular to the direction in which the light beam is transmitted in the Fabry-Perot cavity, and a distance p between one side of the set of opposite sides away from the Fabry-Perot cavity and a straight line passing through the center point of the hexagonal structure is: 0.4m≤p≤0.6m, wherein the straight line is perpendicular to the first diagonal line.

[0056] According to an embodiment of the present disclosure, the length v of a set of opposite sides of the rectangular hole is: ; The length w of the other set of opposite sides of the rectangular hole is: , where d is the width of the Fabry-Perot cavity.

[0057] In the embodiments of the present disclosure, by setting the positional relationship and size relationship of the rectangular holes, the fundamental mode of the coupled cavity structure composed of the whispering gallery microcavity and the FP cavity can obtain the best reflectivity and Q value, and the reflectivity and Q value of the high-order mode are smaller.

[0058] According to an embodiment of the present disclosure, the whispering gallery microcavity includes an N-type confinement layer 6, an active layer 7 and a P-type confinement layer 8 stacked in sequence: wherein the light beam is transmitted from the whispering gallery microcavity to the Fabry-Perot cavity along a direction parallel to the stacked N-type confinement layer, the active layer and the P-type confinement layer.

[0059] According to an embodiment of the present disclosure, it also includes: an N-type substrate 5, which is arranged on a surface of the N-type confinement layer away from the active layer; an N-side electrode 4, which is arranged on a surface of the N-type substrate away from the N-type confinement layer; and an ohmic contact layer 9, which is arranged on a surface of the whispering gallery microcavity away from the N-type substrate and a surface of the Fabry-Perot cavity away from the N-type substrate, wherein an isolation groove is provided between the ohmic contact layers on the whispering gallery microcavity and the Fabry-Perot cavity; and a P-side electrode 10, which is arranged on the ohmic contact layer.

[0060] According to an embodiment of the present disclosure, a rectangular hole is disposed on the whispering gallery microcavity, exposing the N-type substrate underneath and the ohmic contact layer and the P-surface electrode that penetrate the whispering gallery microcavity.

[0061] According to an embodiment of the present disclosure, the shape of the P-side electrode includes a polygon, an arc-edge polygon, a ring, or a circle.

[0062] According to an embodiment of the present disclosure, the internal material of the rectangular hole is benzocyclobutene; benzocyclobutene is provided around the whispering gallery microcavity that does not contain the P-side electrode and around the Fabry-Perot cavity that does not contain the P-side electrode, wherein the refractive index of benzocyclobutene is smaller than the refractive index of the whispering gallery microcavity and the Fabry-Perot cavity material.

[0063] In the embodiment of the present disclosure, the refractive index of benzocyclobutene is smaller than the refractive index of the material used in the coupling cavity, so as to realize the total reflection of the mode in the microcavity, wherein the coupling cavity is composed of a whispering gallery microcavity and a Fabry-Perot cavity.

[0064] According to an embodiment of the present disclosure, the cavity length of the FP cavity is 100 μm-1000 μm.

[0065] According to an embodiment of the present disclosure, the end face of the second end of the FP cavity is a cleaved surface or an end face coating structure.

[0066] Figure 5 Schematic diagram of the first diagonal line of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present invention Schematic diagram of the variation of microcavity mode reflectivity with wavelength when the wavelength is 2.1 μm.

[0067] Figure 6 Schematic diagram of the first diagonal line of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present invention Schematic diagram of the variation of the quality factor of the coupled mode with the wavelength when μm.

[0068] An embodiment of the present disclosure provides a coupled cavity semiconductor laser, wherein a light beam is transmitted to a Fabry-Perot cavity along a whispering gallery microcavity, wherein the cross section of the whispering gallery microcavity is a hexagonal structure, wherein a set of parallel opposite sides in the hexagonal structure is parallel to a first diagonal line in the hexagonal structure, wherein a length m of the set of parallel opposite sides is 12.2 μm, and a length n of the first diagonal line is μm, where the first diagonal line is parallel to the direction of the light beam propagating in the Fabry-Perot cavity.

[0069] A set of opposite sides of the rectangular hole is perpendicular to the direction of light beam transmission in the Fabry-Perot cavity, and a distance p between one side of the set of opposite sides away from the Fabry-Perot cavity and a straight line passing through the center point of the hexagonal structure is 5.9 μm, wherein the straight line is perpendicular to the first diagonal line.

[0070] The length v of one set of opposite sides of the rectangular hole is 1 μm, and the length w of another set of opposite sides of the rectangular hole is 2.5 μm; wherein, the width d of the FP cavity is 1.5 μm, and the length of the FP cavity is 500 μm.

[0071] In the embodiments of the present disclosure, Figure 5As shown in the figure, the reflectivities of the microcavity fundamental modes at 1541nm and 1556nm are 0.79 and 0.83 respectively, and the mode with the highest reflectivity among the high-order modes is located at 1562nm, with a reflectivity of only 0.29. This shows that except for the microcavity fundamental mode, other modes are difficult to couple into the FP cavity, which makes the fundamental mode have an absolute advantage in the competition of microcavity modes, ensuring that the laser can stably output the fundamental mode.

[0072] like Figure 6 As shown in the figure, the finite element simulation of the Q value of the coupling mode formed by the interaction between the whispering gallery mode and the resonant mode of the FP cavity is used to characterize the lasing and anti-feedback capabilities of the coupling mode. The coupling modes formed by the interaction between the fundamental mode and the resonant mode of the FP cavity are located at 1541nm and 1556nm, respectively, and their mode Q values ​​are 14888 and 12744, respectively. At the same time, the Q values ​​of the coupling modes formed by the coupling between the microcavity high-order mode and the FP do not exceed 6000. Therefore, after the formation of the coupling mode, the fundamental mode still occupies a dominant position in the entire coupling cavity and has the characteristics of a high Q value, which ensures that the laser has excellent anti-feedback capabilities.

[0073] Figure 7 Schematic diagram of the first diagonal line of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present disclosure μm, the length of the FP cavity is L = 500 μm, and the injection current in the whispering gallery is I WGM =30mA, FP cavity injection current I FP =Spectrum diagram when 50mA.

[0074] Figure 8 Schematic diagram of the first diagonal line of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present disclosure μm, the length of the FP cavity is L = 400 μm, and the injection current in the whispering gallery is I WGM =30mA, FP cavity injection current I FP =Spectrum diagram when 50mA.

[0075] Fig. 9 The PIV curve of the coupled cavity semiconductor laser when the length L of the FP cavity is 400 μm according to an embodiment of the present disclosure is schematically shown.

[0076] An embodiment of the present disclosure provides a coupled cavity semiconductor laser, wherein a light beam is transmitted to a Fabry-Perot cavity along a whispering gallery microcavity, wherein the cross section of the whispering gallery microcavity is a hexagonal structure, wherein a set of parallel opposite sides in the hexagonal structure is parallel to a first diagonal line in the hexagonal structure, wherein a length m of the set of parallel opposite sides is 10 μm, and a length n of the first diagonal line is μm, where the first diagonal line is parallel to the direction of the light beam propagating in the Fabry-Perot cavity.

[0077] A set of opposite sides of the rectangular hole is perpendicular to the direction of light beam transmission in the Fabry-Perot cavity. The distance p between the side away from the Fabry-Perot cavity and the straight line passing through the center point of the hexagonal structure is 5 μm, where the straight line is perpendicular to the first diagonal line. The length v of a set of opposite sides of the rectangular hole is 1 μm, and the length w of another set of opposite sides of the rectangular hole is 2.6 μm; the width d of the Fabry-Perot cavity is 1.5 μm,

[0078] Inject current I into the whispering gallery area WGM =30mA, FP region injection current I FP =50mA, and detect the corresponding spectra when the length of the FP cavity is 500μm and 400μm respectively.

[0079] In the embodiments of the present disclosure, Figure 7 and Figure 8 As shown in the figure, when the FP cavity length is 500μm and 400μm, the laser has good static characteristics, the side mode suppression is relatively high, and the coupling mode formed by the fundamental mode shows a single-mode lasing state in the spectrum. Fig. 9 It can be seen that when the cavity length of the FP cavity is 400 μm, the single-mode fiber saturation power of the laser is close to 5 mW.

[0080] Fig.10 An anti-feedback testing system according to an embodiment of the present disclosure is schematically shown.

[0081] like Fig.10 As shown, the embodiment of the present disclosure provides a test system for a coupled cavity semiconductor laser, comprising: a DC bias; a laser, a first end of the laser connected to the DC bias; a circulator, a first end of the circulator connected to a second end of the laser; a first beam splitter, a first end of the first beam splitter connected to a second end of the circulator; a polarization controller, a first end of the polarization controller connected to a third end of the circulator; an optical attenuator, a first end of the optical attenuator connected to a second end of the first beam splitter; a second beam splitter, a first end of the second beam splitter connected to a second end of the optical attenuator, and a second end of the second beam splitter connected to a polarization controller. a power meter connected to the third end of the second spectrometer; a third spectrometer, a first end of the third spectrometer connected to the third end of the first spectrometer; a spectrometer, a spectrometer connected to the second end of the third spectrometer; a photodetector, a first end of the photodetector connected to the third end of the third spectrometer; a DC bias device, a first end of the DC bias device connected to the second end of the photodetector; an electric amplifier, a first end of the electric amplifier connected to the second end of the DC bias device; a spectrum analyzer, a spectrum analyzer connected to the second end of the electric amplifier; and a multimeter, the multimeter connected to the third end of the DC bias device.

[0082] In the embodiment of the present disclosure, current is applied to the whispering gallery microcavity and FP cavity of the laser respectively by the method of partitioned electrical injection, and the output light of the laser is coupled into the anti-feedback test system through a single-mode optical fiber. The optical power coupled into the system is defined as P0, which is divided into two branches by a 1:1 first optical splitter after passing through a circulator CIR. The branch above it is used to form optical feedback. The light first passes through the optical attenuator VOA to adjust the light intensity fed back to the laser by the system. The light after passing through the polarization controller PC is split by the 1:9 second optical splitter. One path is used to detect the power fed back to the system, and its size is recorded as P1. The other path passes through the optical polarization controller PM to adjust the polarization direction of the feedback light to be exactly the same as the polarization state of the incident light, so as to ensure the maximum impact on the original mode of the laser. The light with adjusted polarization state is re-injected into the laser Laser through the circulator CIR, where the power of the feedback light is defined as P2, P2=9P1. The branch on the right is used to test the spectrum and frequency noise after the laser feedback, and characterize the actual performance of the laser working under feedback.

[0083] In the feedback test system, the feedback intensity is defined as the ratio of the feedback light power P2 to the single-mode fiber coupling power P0. At the same time, we will determine whether the laser enters the coherent collapse state by testing relative intensity noise or spectrum, and define the feedback intensity when it is about to enter the coherent collapse state as the anti-feedback threshold of this coupled cavity laser.

[0084] Among them, DC bias is Direct Current Bias, referred to as DC Bias; laser is Light Amplification by Stimulated Emission of Radiation, referred to as Laser; circulator is Circulator, referred to as CIR; polarization controller is Polarization Controller, referred to as PC; power meter is Power Meter, referred to as PM; optical attenuator is Variable Optical Attenuator, referred to as VOA; spectrometer is Optical Spectrum Analyzer, referred to as OSA; photodetector is Photodetector, referred to as PD; DC bias is BiasTee, referred to as Bias-T; spectrum analyzer is Electrical Spectrum Analyzer, referred to as ESA; multimeter is Digital Multimeter, referred to as DMM; electrical amplifier is Amplifier; the first splitter is Optical Splitter, referred to as OS1, the second splitter is Optical Splitter, referred to as OS2; the third splitter is Optical Splitter, referred to as OS3.

[0085] Fig.11 Schematic diagram of the first diagonal line of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present disclosure μm, the length of the FP cavity is L = 500 μm, and the injection current in the whispering gallery is I WGM =30mA, FP cavity injection current I FP Schematic diagram of the output spectrum changing with feedback intensity when =50mA.

[0086] Fig.12 Schematic diagram of the first diagonal line of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present disclosure μm, the length of the FP cavity is L = 400 μm, and the injection current in the whispering gallery is I WGM =30mA, FP cavity injection current I FP Schematic diagram of the output spectrum changing with feedback intensity when =50mA.

[0087] In the embodiments of the present disclosure, using Fig.10 Anti-feedback system test shown Figure 7 The anti-feedback threshold of the coupled cavity semiconductor laser in the corresponding embodiment is as follows: Fig.11 As shown in the figure, when the feedback intensity is low, the laser exhibits a single-mode lasing state, and the lasing peak is located at 1541nm. As the feedback intensity increases, the laser enters a coherent collapse state, showing obvious spectral broadening in the spectral thermogram, and its anti-feedback threshold is -14.5dB. Fig.10 Anti-feedback system test shown Fig.12 The anti-feedback threshold of the coupled cavity semiconductor laser in the corresponding embodiment is as follows: Fig.11 As shown, the anti-feedback threshold of the laser is -14dB, which is improved compared with the laser with a FP cavity length of 500μm.

[0088] Fig.13 Schematic diagram of the first diagonal line of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present disclosure μm, the length of the FP cavity is L = 400 μm, and the injection current in the whispering gallery is I WGM =30mA, FP cavity injection current I FP Schematic diagram of the output spectrum changing with feedback intensity when =50mA.

[0089] An embodiment of the present disclosure provides a coupled cavity semiconductor laser, wherein a light beam is transmitted to a Fabry-Perot cavity along a whispering gallery microcavity, wherein the cross section of the whispering gallery microcavity is a hexagonal structure, wherein a set of parallel opposite sides in the hexagonal structure is parallel to a first diagonal line in the hexagonal structure, wherein a length m of the set of parallel opposite sides is 10 μm, and a length n of the first diagonal line is μm, where the first diagonal line is parallel to the direction of the light beam propagating in the Fabry-Perot cavity.

[0090] A set of opposite sides of the rectangular hole is perpendicular to the direction of light beam transmission in the Fabry-Perot cavity, and the distance p between one side of the set of opposite sides away from the Fabry-Perot cavity and the straight line passing through the center point of the hexagonal structure is 5 μm, where the straight line is perpendicular to the first diagonal line. The length v of a set of opposite sides of the rectangular hole is 1 μm, and the length w of another set of opposite sides of the rectangular hole is 2.6 μm; where the width d of the Fabry-Perot cavity is 1.5 μm.

[0091] In the embodiments of the present disclosure, using Fig.10 The anti-feedback system shown in the figure tests the anti-feedback threshold of the coupled cavity semiconductor laser in the embodiment of the present disclosure. Fig.13 As shown, the anti-feedback threshold of the laser can reach -12.5dB, compared with Fig.12 As shown, the anti-feedback threshold of the laser is -14dB. By controlling the size of the whispering gallery microcavity, the anti-feedback threshold of the laser can be effectively increased, thereby improving the anti-feedback capability.

[0092] Therefore, the coupled cavity semiconductor laser disclosed in the present invention has the advantages of small size, simple structure, no need for secondary epitaxy or high-precision lithography preparation, etc. The present invention optimizes the mode distribution in the whispering gallery microcavity, so that the whispering gallery fundamental mode with a high Q value occupies a dominant position in the microcavity, and can then interact with the mode in the FP cavity to form a coupled mode with a high Q value characteristic. And the above results show that the laser of this structure has good static characteristics, and the anti-feedback threshold of the designed anti-feedback coupled cavity semiconductor laser can reach -12.5dB, and by further increasing the size of the whispering gallery mode microcavity and increasing the proportion of photons in the microcavity, the anti-feedback threshold of the laser is further improved. This result has been significantly improved compared to other coupled cavity lasers, and can meet the needs of most practical applications such as on-chip light sources and optical modules.

[0093] It will be appreciated by those skilled in the art that the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations and / or combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways without departing from the spirit and teachings of the present disclosure. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0094] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. The scope of the present disclosure is defined by the attached claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A coupled cavity semiconductor laser, characterized in that: include: Whispering gallery microcavity, used to output the whispering gallery fundamental mode; A Fabry-Perot cavity, wherein a first end of the Fabry-Perot cavity is connected to the whispering gallery microcavity; The resonant mode of the Fabry-Perot cavity is coupled with the fundamental mode of the whispering gallery, and a light beam of the coupled mode is output from the second end of the Fabry-Perot cavity.

2. The coupled cavity semiconductor laser according to claim 1, characterized in that: The light beam is transmitted to the Fabry-Perot cavity along the whispering gallery microcavity, the cross section of the whispering gallery microcavity is a hexagonal structure, a set of parallel opposite sides in the hexagonal structure is parallel to the first diagonal line in the hexagonal structure, and the length m of the set of parallel opposite sides is: ， Wherein, n is the length of the first diagonal line, and the first diagonal line is parallel to the direction in which the light beam is transmitted in the Fabry-Perot cavity.

3. The coupled cavity semiconductor laser according to claim 2, characterized in that: The whispering gallery microcavity comprises: A rectangular hole is arranged on the whispering gallery microcavity to suppress the high-order modes of the whispering gallery microcavity.

4. The coupled cavity semiconductor laser according to claim 3, characterized in that: A set of opposite sides of the rectangular hole is perpendicular to the direction in which the light beam is transmitted in the Fabry-Perot cavity, and a distance p between one side of the set of opposite sides away from the Fabry-Perot cavity and a straight line passing through the center point of the hexagonal structure is: , wherein the straight line is perpendicular to the first diagonal line.

5. The coupled cavity semiconductor laser according to claim 4, characterized in that: The length v of a set of opposite sides of the rectangular hole is: ; The length w of the other set of opposite sides of the rectangular hole is: , where d is the width of the Fabry-Perot cavity.

6. The coupled cavity semiconductor laser according to claim 3, characterized in that: The whispering gallery microcavity comprises an N-type confinement layer, an active layer and a P-type confinement layer which are stacked in sequence: The light beam is transmitted from the whispering gallery microcavity to the Fabry-Perot cavity along a direction parallel to the stacked N-type confinement layer, the active layer and the P-type confinement layer.

7. The coupled cavity semiconductor laser according to claim 6, characterized in that: Also includes: An N-type substrate is disposed on a surface of the N-type confinement layer away from the active layer; An N-side electrode is disposed on a surface of the N-type substrate away from the N-type restriction layer; as well as An ohmic contact layer is provided on a surface of the whispering gallery microcavity away from the N-type substrate and a surface of the Fabry-Perot cavity away from the N-type substrate, wherein the ohmic contact layers on the whispering gallery microcavity and the Fabry-Perot cavity are provided with isolation grooves; The P-side electrode is arranged on the ohmic contact layer.

8. The coupled cavity semiconductor laser according to claim 7, characterized in that: The shape of the P-side electrode includes a polygon, an arc-edge polygon, a ring or a circle.

9. The coupled cavity semiconductor laser according to claim 7, characterized in that: The inner material of the rectangular hole is benzocyclobutene; Benzocyclobutene is provided around the whispering gallery microcavity without the P-side electrode and around the Fabry-Perot cavity without the P-side electrode, wherein the refractive index of the benzocyclobutene is smaller than the refractive index of the whispering gallery microcavity and the Fabry-Perot cavity material.

10. A test system for a coupled cavity semiconductor laser according to any one of claims 1 to 9, characterized in that: include: DC bias; A laser, a first end of the laser being connected to the DC bias; a circulator, a first end of the circulator being connected to a second end of the laser; a first beam splitter, wherein a first end of the first beam splitter is connected to a second end of the circulator; a polarization controller, a first end of the polarization controller being connected to a third end of the circulator; an optical attenuator, a first end of the optical attenuator being connected to the second end of the first optical splitter; A second optical splitter, wherein a first end of the second optical splitter is connected to a second end of the optical attenuator, and a second end of the second optical splitter is connected to a second end of the polarization controller; a power meter connected to the third end of the second optical splitter; a third optical splitter, wherein a first end of the third optical splitter is connected to a third end of the first optical splitter; a spectrometer connected to the second end of the third spectrometer; a photodetector, wherein a first end of the photodetector is connected to a third end of the third beam splitter; A DC bias device, wherein a first end of the DC bias device is connected to a second end of the photodetector; an electrical amplifier, wherein a first end of the electrical amplifier is connected to a second end of the DC bias device; A spectrum analyzer connected to the second end of the electrical amplifier; as well as A multimeter is connected to the third terminal of the DC bias device.

Images