Coupled cavity semiconductor laser

Abstract

This disclosure provides a coupled-cavity semiconductor laser, relating to the fields of fiber optic communication and semiconductor laser technology. The coupled-cavity semiconductor laser includes: a whispering-gallery microcavity for outputting a whispering-gallery fundamental mode; and a Fabry-Perot cavity, a first end of which is connected to the whispering-gallery microcavity; wherein the resonant mode of the Fabry-Perot cavity is coupled to the whispering-gallery fundamental mode, and a coupled-mode beam is output from a second end of the Fabry-Perot cavity.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of optical fiber communication and semiconductor laser technology, and more particularly, to a coupled cavity semiconductor laser. BACKGROUND

[0002] Semiconductor lasers are important components in optical fiber communication systems and on-chip photonic integrated chips, and inevitably suffer from optical feedback from other elements or end faces in the system. The laser is sensitive to external optical feedback, and when the feedback intensity is large, the single-mode laser will enter a coherent collapse state from a single-mode output state, and then phenomena such as increase in intensity noise, linewidth widening and mode hopping will occur, which is particularly harmful to the communication system and can cause problems such as increase in bit error rate and crosstalk of pulse sequences. SUMMARY

[0003] Therefore, the present disclosure provides a coupled cavity semiconductor laser, comprising: a whispering gallery microcavity configured to output a whispering gallery mode; and a Fabry-Perot cavity, a first end of the Fabry-Perot cavity being connected to the whispering gallery microcavity; wherein a resonance mode of the Fabry-Perot cavity is coupled to the whispering gallery mode, and a light beam of the coupled mode is output from a second end of the Fabry-Perot cavity.

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

[0005] ,

[0006] wherein n is a length of the first diagonal line, and the first diagonal line is parallel to a 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 comprises: a rectangular hole arranged on the whispering gallery microcavity and configured to suppress a high-order mode 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 a distance p from one side of the set of opposite sides to a straight line passing through a 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, a length v of the set of opposite sides of the rectangular hole is: and a length w of another set of opposite sides of the rectangular hole is: wherein d is a width of the Fabry-Perot cavity.

[0010] According to an embodiment of the present disclosure, the whispering gallery microcavity comprises an N-type confinement layer, an active layer and a P-type confinement layer which are sequentially stacked; a 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, active layer and P-type confinement layer. According to an embodiment of the present disclosure, further comprising: an N-type substrate arranged on a surface of the N-type confinement layer away from the active layer; an N-face electrode arranged on a surface of the N-type substrate away from the N-type confinement layer; and an ohmic contact layer arranged on a surface of the whispering gallery microcavity away from the N-type substrate and on a surface of the Fabry-Perot cavity away from the N-type substrate, wherein an isolation groove is arranged between the ohmic contact layers on the whispering gallery microcavity and the Fabry-Perot cavity; and a P-face electrode arranged on the ohmic contact layer.

[0011] According to an embodiment of the present disclosure, the shape of the P-face electrode comprises a polygon, an arc-edged polygon, a circular ring or a circle.

[0012] According to an embodiment of the present disclosure, the inner material of the rectangular hole is benzocyclobutene; the four sides of the P-face electrode of the whispering gallery microcavity and the four sides of the P-face electrode of the Fabry-Perot cavity are provided with benzocyclobutene, wherein the refractive index of the benzocyclobutene is less than the refractive index of the materials of the whispering gallery microcavity and the Fabry-Perot cavity.

[0013] A test system for a coupled cavity semiconductor laser, comprising: a direct current bias; a laser, a first end of the laser being connected with the direct current bias; a circulator, a first end of the circulator being connected with a second end of the laser; a first optical splitter, a first end of the first optical splitter being connected with a second end of the circulator; a polarization controller, a first end of the polarization controller being connected with a third end of the circulator; an optical attenuator, a first end of the optical attenuator being connected with a second end of the first optical splitter; a second optical splitter, a first end of the second optical splitter being connected with a second end of the optical attenuator, and a second end of the second optical splitter being connected with a second end of the polarization controller; a power meter, the power meter being connected with a third end of the second optical splitter; a third optical splitter, a first end of the third optical splitter being connected with a third end of the first optical splitter; a spectrometer, the spectrometer being connected with a second end of the third optical splitter; a photodetector, a first end of the photodetector being connected with a third end of the third optical splitter; a direct current biaser, a first end of the direct current biaser being connected with a second end of the photodetector; an electrical amplifier, a first end of the electrical amplifier being connected with a second end of the direct current biaser; a frequency spectrometer, the frequency spectrometer being connected with a second end of the electrical amplifier; and a multimeter, the multimeter being connected with a third end of the direct current biaser.

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

[0015] According to an embodiment of the present disclosure, by designing the light beam 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, which can simplify the mode-chaotic reflection spectrum envelope in the microcavity when the cross section is simplified as a square, so that only the fundamental mode and a set of high-order mode envelopes are present between two sets of adjacent longitudinal modes of the microcavity, have a relatively high mode reflectivity, and make the mode in the microcavity more pure.

[0016] According to an embodiment of the present disclosure, by designing the rectangular hole, the light field distribution of the high-order mode is destroyed, which can sufficiently lower the reflectivity of the high-order mode while not changing the reflectivity of the fundamental mode, so that in a free spectral range, the fundamental mode of the whispering gallery microcavity has an absolute advantage in mode competition, and then can interact with the resonant mode in the Fabry-Perot cavity to form a coupled mode, so that the microcavity laser can realize stable single-mode lasing and has excellent static and dynamic characteristics. BRIEF DESCRIPTION OF DRAWINGS

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

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

[0019] Figure 2 A top view of a coupled-cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown;

[0020] Figure 3 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 is schematically shown;

[0021] Figure 4 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 is schematically shown;

[0022] Figure 5 A diagram of a first diagonal line n = 18 μm, a diagram of microcavity mode reflectivity changing with wavelength of a whispering gallery microcavity of a coupled-cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown;

[0023] Figure 6 A diagram of a first diagonal line n = 18 μm, a diagram of quality factor of a coupled mode changing with wavelength of a whispering gallery microcavity of a coupled-cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown;

[0024] Figure 7Spectrogram of the coupled-cavity semiconductor laser according to an embodiment of the present disclosure when the length of the FP cavity L = 500 μm, the length of the whispering gallery microcavity L = 500 μm, the injection current of the whispering gallery region I = 30 mA, and the injection current of the FP cavity I = 50 mA μm, the length of the FP cavity L = 400 μm, the injection current of the whispering gallery region I = 30 mA, and the injection current of the FP cavity I = 50 mA WGM = 30 mA, and the injection current of the FP cavity I = 50 mA FP = 30 mA, and the injection current of the FP cavity I = 50 mA

[0025] Figure 8 Spectrogram of the coupled-cavity semiconductor laser according to an embodiment of the present disclosure when the length of the FP cavity L = 500 μm, the length of the whispering gallery microcavity L = 500 μm, the injection current of the whispering gallery region I = 30 mA, and the injection current of the FP cavity I = 50 mA μm, the length of the FP cavity L = 400 μm, the injection current of the whispering gallery region I = 30 mA, and the injection current of the FP cavity I = 50 mA WGM = 30 mA, and the injection current of the FP cavity I = 50 mA FP = 30 mA, and the injection current of the FP cavity I = 50 mA

[0026] Figure 9 PIV curve of the coupled-cavity semiconductor laser when the length of the FP cavity L = 400 μm according to an embodiment of the present disclosure

[0027] Figure 10 Anti-feedback test system according to an embodiment of the present disclosure

[0028] Figure 11 Spectrogram of the coupled-cavity semiconductor laser according to an embodiment of the present disclosure when the length of the FP cavity L = 500 μm, the length of the whispering gallery microcavity L = 500 μm, the injection current of the whispering gallery region I = 30 mA, and the injection current of the FP cavity I = 50 mA μm, the length of the FP cavity L = 400 μm, the injection current of the whispering gallery region I = 30 mA, and the injection current of the FP cavity I = 50 mA WGM = 30 mA, and the injection current of the FP cavity I = 50 mA FP = 30 mA, and the injection current of the FP cavity I = 50 mA

[0029] Figure 12 Spectrogram of the coupled-cavity semiconductor laser according to an embodiment of the present disclosure when the length of the FP cavity L = 500 μm, the length of the whispering gallery microcavity L = 500 μm, the injection current of the whispering gallery region I = 30 mA, and the injection current of the FP cavity I = 50 mA μm, the length of the FP cavity L = 400 μm, the injection current of the whispering gallery region I = 30 mA, and the injection current of the FP cavity I = 50 mA WGM = 30 mA, and the injection current of the FP cavity I = 50 mA FP = 30 mA, and the injection current of the FP cavity I = 50 mA

[0030] Figure 13 Spectrogram of the coupled-cavity semiconductor laser according to an embodiment of the present disclosure when the length of the FP cavity L = 500 μm, the length of the whispering gallery microcavity L = 500 μm, the injection current of the whispering gallery region I = 30 mA, and the injection current of the FP cavity I = 50 mA μm, the length of the FP cavity L = 400 μm, the injection current of the whispering gallery region I = 30 mA, and the injection current of the FP cavity I = 50 mA WGM = 30 mA, and the injection current of the FP cavity I = 50 mA FP = 30 mA, and the injection current of the FP cavity I = 50 mA

[0031] Reference Signs List:

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

[0033] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It is to be understood, however, that the description is merely exemplary and is not intended to limit the scope of the present disclosure. In the following detailed description of the embodiments of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. However, it would be apparent to those skilled in the art that the embodiments of the present disclosure can be practiced without these specific details. In other instances, well-known structures and functions have not been described in detail in order not to unnecessarily obscure aspects of the present disclosure.

[0034] The terms used herein are merely used to describe specific embodiments, and are not intended to limit the present disclosure. The terms "include" and "have" and the like used herein indicate the presence of the features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0035] All terms used herein, including technical and scientific terms, have the same meanings as those generally understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having meanings consistent with the context of the present description, and should not be interpreted in an idealized or excessively formal manner.

[0036] In the case of using expressions similar to "at least one of A, B, and C, etc.", it should generally be interpreted to include at least one of each item enumerated, but not to exclude others not enumerated. For example, "a system having at least one of A, B, and C" should be interpreted to include systems having at least one of A, B, or C, systems having at least one of A and B, systems having at least one of A and C, systems having at least one of B and C, systems having all of A, B, and C, etc.

[0037] The most common method currently used to avoid the influence of optical feedback on a laser is to introduce an isolator. For the field of optical fiber communication, this increases the size of the device, reduces the output power, increases the difficulty of packaging, and greatly increases the cost of the system. For the field of photonic integration, there is currently 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 the laser is currently a hot topic of research.

[0038] The related research shows that the coherent collapse threshold of the semiconductor laser is inversely proportional to the fourth power of the effective linewidth enhancement factor, so using a material with a lower effective linewidth enhancement factor or reasonably designing the structure of the laser can effectively improve the anti-feedback ability of the laser. Compared with the quantum well laser, the quantum dot laser has better anti-feedback performance, but due to its higher difficulty in preparation, the comprehensive performance is still slightly inferior to the quantum well laser. The related theoretical and experimental researches show that the anti-feedback ability of the laser can be effectively improved by improving the quality factor (Q value) of the lasing mode of the laser, but the structure of the traditional quantum well laser is often difficult to effectively improve the mode Q value.

[0039] The coupled cavity laser has a high Q value echo wall mode microcavity, and the feedback light is not easy to affect the original lasing coupling mode, which makes the coupled cavity laser attract much attention in the field of anti-feedback research.

[0040] The lasing mode of the common coupled cavity laser is often a coupled mode formed by coupling the high-order echo wall mode of the microcavity and the resonant mode of the Fabry-Perot cavity (FP cavity), because the high-order mode reflection peak is wider and easier to form good mode matching with the resonant mode of the FP cavity. However, compared with the coupled mode formed by the echo wall base mode, the coupled mode formed by the high-order mode has a lower Q value, and the improvement of the anti-feedback ability of the laser is limited.

[0041] At the same time, the microcavity mode in the existing square or rhombus coupled cavity laser is extremely complex, and the base mode with a high Q value in the laser has no advantage in the mode competition of the microcavity, so the actual lasing is often a low-Q high-order coupled mode, which makes the anti-feedback ability of the coupled cavity laser cannot be further improved.

[0042] Based on this, the echo wall microcavity outputs the echo wall base mode with a high quality factor and the resonant mode of the FP cavity, and then outputs the coupled mode with a high Q value, thereby greatly improving the anti-feedback ability and comprehensive output performance of the laser.

[0043] Figure 1 A perspective structure schematic diagram of a 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] As Figure 1 and Figure 2As shown, the coupling-cavity semiconductor laser provided by the embodiment can include: an echo-wall microcavity 1 configured to output an echo-wall base mode; and a Fabry-Perot cavity 2, a first end of the Fabry-Perot cavity being connected to the echo-wall microcavity; wherein a resonance mode of the Fabry-Perot cavity is coupled to the echo-wall base mode, and a light beam of a coupling mode is output from a second end of the Fabry-Perot cavity.

[0046] In the embodiment of the present disclosure, the external light beam enters the echo-wall microcavity after being incident from the second end of the FP cavity, and is reflected multiple times in the echo-wall microcavity and then exits from the second end surface of the FP cavity. The embodiment couples the echo-wall base mode with high quality factor output by the echo-wall microcavity to the resonance mode of the FP cavity, and then outputs the coupling mode with high Q value, thereby greatly improving the anti-feedback capability and comprehensive output performance of the laser.

[0047] According to the embodiment of the present disclosure, the light beam is transmitted along the echo-wall microcavity to the Fabry-Perot cavity, the cross section of the echo-wall microcavity is a hexagonal structure, a group of parallel opposite sides in the hexagonal structure is parallel to a first diagonal line in the hexagonal structure, and the length m of the group 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 embodiment of the present disclosure, the hexagonal structure is a square shape with a group of opposite corners cut off, and by controlling the cross section of the echo-wall microcavity to be a hexagonal structure in the direction in which the light beam is transmitted along the echo-wall microcavity to the Fabry-Perot cavity, the microcavity reflection spectrum envelope can be made more simple, and in a free frequency spectrum range, there is only a group of base modes and a group of high-order mode envelopes, which have relatively high mode reflectivity, so that the modes in the microcavity are more pure.

[0051] Figure 3 A mode field distribution diagram of a base mode in an echo-wall microcavity of a coupling-cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown.

[0052] Figure 4 A mode field distribution diagram of a high-order mode in an echo-wall microcavity of a coupling-cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown.

[0053] According to the embodiment of the present disclosure, the echo-wall microcavity includes: a rectangular hole 3 arranged on the echo-wall microcavity and configured to suppress high-order modes of the echo-wall microcavity.

[0054] In the embodiment of the present disclosure, as shown in Figure 3 and Figure 4As shown, the high-order mode of the whispering gallery microcavity is more concentrated in the center of the microcavity, and the mode field center of the microcavity base mode is weak, so by setting the rectangular hole in the position with high mode distribution intensity, the high-order mode is effectively suppressed while the base mode reflection and Q value are almost not affected, so that the high-Q base mode can realize stable single-mode emission.

[0055] According to an embodiment of the present disclosure, one pair of opposite sides of the rectangular hole is perpendicular to the direction of the light beam transmitted in the Fabry-Perot cavity, and the distance p from one side of the pair of opposite sides to 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 one pair of opposite sides of the rectangular hole is: The length w of the other pair of opposite sides of the rectangular hole is: wherein d is the width of the Fabry-Perot cavity.

[0057] In an embodiment of the present disclosure, by setting the position relationship and size relationship of the rectangular hole, the base 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 small.

[0058] According to an embodiment of the present disclosure, the whispering gallery microcavity comprises an N-type confinement layer 6, an active layer 7 and a P-type confinement layer 8 which are sequentially stacked: 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, active layer and P-type confinement layer.

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

[0060] According to an embodiment of the present disclosure, the rectangular hole is arranged on the whispering gallery microcavity and exposes the underlying N-type substrate and the ohmic contact layer and P-face electrode above the whispering gallery microcavity.

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

[0062] According to an embodiment of the present disclosure, the inner material of the rectangular hole is benzocyclobutene; the periphery of the whispering gallery microcavity without a P-face electrode and the periphery of the Fabry-Perot cavity without a P-face electrode are provided with benzocyclobutene, wherein the refractive index of the benzocyclobutene is less than the refractive index of the materials of the whispering gallery microcavity and the Fabry-Perot cavity.

[0063] In an embodiment of the present disclosure, the refractive index of the benzocyclobutene is less than the refractive index of the material of the coupling cavity, which is composed of the whispering gallery microcavity and the Fabry-Perot cavity, for realizing total reflection of the mode in the microcavity.

[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 end face or an end face coated with a film.

[0066] Figure 5 The first diagonal line of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown. The schematic diagram of the wavelength variation of the microcavity mode reflectivity when the length of the FP cavity is 500 μm is shown.

[0067] Figure 6 The first diagonal line of the whispering gallery microcavity of the coupled cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown. The schematic diagram of the wavelength variation of the quality factor of the coupling mode when the length of the FP cavity is 500 μm is shown.

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

[0069] A group of opposite sides of the rectangular hole is perpendicular to the direction of the light beam transmission in the Fabry-Perot cavity, and the distance p between one side of the group of opposite sides far 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 the group of opposite sides of the rectangular hole is 1 μm, and the length w of the other group 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 an embodiment of the present disclosure, as Figure 5As shown, the reflectivities of the microcavity fundamental mode at 1541nm and 1556nm are 0.79 and 0.83, respectively. Among the higher-order modes, the mode with the highest reflectivity is located at 1562nm, with a reflectivity of only 0.29. This indicates that, apart from the microcavity fundamental mode, other modes are difficult to couple into the FP cavity. This gives the fundamental mode an absolute advantage in the competition among microcavity modes, ensuring that the laser can stably output the fundamental mode.

[0072] like Figure 6 As shown, the lasing behavior and anti-feedback capability of the coupled modes are characterized by finite element simulation of the Q-values ​​of the coupled modes formed by the interaction between the whispering-gallery mode and the resonant mode of the FP cavity. The coupled modes formed by the interaction between the fundamental mode and the resonant mode of the FP cavity are located at 1541 nm and 1556 nm, respectively, with Q-values ​​of 14888 and 12744. Meanwhile, the Q-values ​​of the coupled modes formed by the coupling of the higher-order modes of the microcavity and the FP cavity do not exceed 6000. Therefore, after the fundamental mode forms the coupled modes, it still dominates the entire coupled cavity and has a high Q-value, ensuring that the laser has excellent anti-feedback capability.

[0073] Figure 7 The first diagonal of the whispering-gallery microcavity of a coupled-cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown. μm, FP cavity length L=500μm, whispering galvanic injection current I WGM =30mA, FP cavity injection current I FP Spectrum at 50mA.

[0074] Figure 8 The first diagonal of the whispering-gallery microcavity of a coupled-cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown. μm, FP cavity length L=400μm, whispering galvanic injection current I WGM =30mA, FP cavity injection current I FP Spectrum at 50mA.

[0075] Figure 9 The diagram schematically illustrates the PIV curve of a coupled-cavity semiconductor laser with a cavity length L=400μm according to an embodiment of the present disclosure.

[0076] One embodiment of this disclosure provides a coupled-cavity semiconductor laser in which the beam is transmitted along a whispering-gallery microcavity to a Fabry-Perot cavity. The whispering-gallery microcavity has a hexagonal cross-section, with a set of parallel sides parallel to the first diagonal. The length m of the set of parallel sides is 10 μm, and the length n of the first diagonal is... μm, where the first diagonal is parallel to the direction of beam propagation in the Fabry-Perot cavity.

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

[0078] injecting a current I in the whispering gallery region WGM = 30 mA, and injecting a current I FP = 50 mA, and detecting the corresponding spectral diagram when the length of the FP cavity is 500 μm and 400 μm, respectively.

[0079] In the embodiments of the present disclosure, as shown in Figure 7 and Figure 8 When the cavity length of the FP cavity is 500 μm and 400 μm, the laser has good static characteristics, the side mode suppression is relatively high, and the coupling mode formed by the fundamental mode presents a single mode lasing state in the spectrum. Figure 9 It can be known 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] Figure 10 The anti-feedback test system according to the embodiments of the present disclosure is schematically shown.

[0081] As shown in Figure 10 The embodiments of the present disclosure provide a test system for a coupled cavity semiconductor laser, which comprises a direct current bias, a laser, a first end of the laser being connected with the direct current bias, a circulator, a first end of the circulator being connected with a second end of the laser, a first beam splitter, a first end of the first beam splitter being connected with a second end of the circulator, a polarization controller, a first end of the polarization controller being connected with a third end of the circulator, an optical attenuator, a first end of the optical attenuator being connected with a second end of the first beam splitter, a second beam splitter, a first end of the second beam splitter being connected with a second end of the optical attenuator, a second end of the second beam splitter being connected with a second end of the polarization controller, a power meter, the power meter being connected with a third end of the second beam splitter, a third beam splitter, a first end of the third beam splitter being connected with a third end of the first beam splitter, a spectrometer, the spectrometer being connected with a second end of the third beam splitter, a photodetector, a first end of the photodetector being connected with a third end of the third beam splitter, a direct current biasing device, a first end of the direct current biasing device being connected with a second end of the photodetector, an electrical amplifier, a first end of the electrical amplifier being connected with a second end of the direct current biasing device, a frequency spectrometer, the frequency spectrometer being connected with a second end of the electrical amplifier, and a multimeter, a third end of the direct current biasing device being connected with the multimeter.

[0082] In the embodiments of the present disclosure, the method of partitioned electrical injection respectively applies current to the whispering gallery microcavity and the FP cavity of the laser, and the output light of the laser is coupled into an anti-feedback test system through a single-mode fiber, and 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 upper branch is used to form optical feedback. The light first passes through an optical attenuator VOA to adjust the optical intensity of the system feedback to the laser, and the light after passing through a polarization controller PC is split by a 1:9 second optical splitter, one branch is used to detect the power of the feedback to the system, and the size is recorded as P1, and the other branch passes through a light 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 greatest influence on the original mode of the laser. The light with adjusted polarization state is injected into the laser Laser again through the circulator CIR, wherein the power of the feedback light is defined as P2, P2=9P1. The right branch is used to test the spectrum and frequency noise of the laser after feedback, which represents the actual performance of the laser under feedback.

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

[0084] Wherein, Direct Current Bias is DC Bias for short; Light Amplification by Stimulated Emission of Radiation is Laser for short; Circulator is CIR for short; Polarization Controller is PC for short; Power Meter is PM for short; Variable Optical Attenuator is VOA for short; Optical Spectrum Analyzer is OSA for short; Photodetector is PD for short; Bias Tee is Bias-T for short; Electrical Spectrum Analyzer is ESA for short; Digital Multimeter is DMM for short; Amplifier is; Optical Splitter is OS1 for short, and Optical Splitter is OS2 for short; Optical Splitter is OS3 for short.

[0085] Figure 11 The first diagonal of the whispering-gallery microcavity of a coupled-cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown. μm, FP cavity length L=500μm, whispering galvanic injection current I WGM =30mA, FP cavity injection current I FP A schematic diagram showing how the output spectrum changes with the feedback intensity at 50mA.

[0086] Figure 12 The first diagonal of the whispering-gallery microcavity of a coupled-cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown. μm, FP cavity length L=400μm, whispering galvanic injection current I WGM =30mA, FP cavity injection current I FP A schematic diagram showing how the output spectrum changes with the feedback intensity at 50mA.

[0087] In the embodiments of this disclosure, utilizing Figure 10 The anti-feedback system test shown Figure 7 The feedback rejection threshold of the coupled-cavity semiconductor laser in the corresponding embodiment, such as Figure 11 As shown, when the feedback intensity is low, the laser exhibits a single-mode lasing state with a lasing peak at 1541 nm. With increasing feedback intensity, the laser enters a coherent collapse state, exhibiting significant spectral broadening in the thermo-spectral diagram, with an anti-feedback threshold of -14.5 dB. Using... Figure 10 The anti-feedback system test shown Figure 12 The feedback rejection threshold of the coupled-cavity semiconductor laser in the corresponding embodiment, such as Figure 11 As shown, the anti-feedback threshold of the laser is -14dB, which is an improvement compared to the laser with a FP cavity length of 500μm.

[0088] Figure 13 The first diagonal of the whispering-gallery microcavity of a coupled-cavity semiconductor laser according to an embodiment of the present disclosure is schematically shown. μm, FP cavity length L=400μm, whispering galvanic injection current I WGM =30mA, FP cavity injection current I FP A schematic diagram showing how the output spectrum changes with the feedback intensity at 50mA.

[0089] One embodiment of this disclosure provides a coupled-cavity semiconductor laser in which the beam is transmitted along a whispering-gallery microcavity to a Fabry-Perot cavity. The whispering-gallery microcavity has a hexagonal cross-section, with a set of parallel sides parallel to the first diagonal. The length m of the set of parallel sides is 10 μm, and the length n of the first diagonal is... μm, where the first diagonal is parallel to the direction of beam propagation in the Fabry-Perot cavity.

[0090] One pair of opposite sides of the rectangular aperture is perpendicular to the direction of beam propagation in the Fabry-Perot cavity. The distance p between the side of the pair of opposite sides furthest 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. The length v of one pair of opposite sides of the rectangular aperture is 1 μm, and the length w of the other pair of opposite sides of the rectangular aperture is 2.6 μm; the width d of the Fabry-Perot cavity is 1.5 μm.

[0091] In the embodiments of this disclosure, utilizing Figure 10 The feedback resistance system shown tests the feedback resistance threshold of the coupled-cavity semiconductor laser in the embodiments of this disclosure, such as... Figure 13 As shown, the laser's anti-feedback threshold can reach -12.5dB, compared to Figure 12 As shown, the anti-feedback threshold of the laser is -14dB. By controlling the size of the whispering galvanic microcavity, the anti-feedback threshold of the laser can be effectively improved, thereby enhancing its anti-feedback capability.

[0092] Therefore, the coupled-cavity semiconductor laser disclosed herein possesses advantages such as small size, simple structure, and no need for secondary epitaxy or high-precision photolithography fabrication. This disclosure optimizes the mode distribution in the whispering-gallery microcavity, allowing the high-Q whispering-gallery fundamental mode to dominate the microcavity, thereby interacting with modes in the FP cavity to form coupled modes with high-Q characteristics. Furthermore, the above results demonstrate that the laser with this structure exhibits excellent static characteristics, and the designed anti-feedback coupled-cavity semiconductor laser achieves an anti-feedback threshold of -12.5 dB. By further increasing the size of the whispering-gallery mode microcavity and improving the photon count ratio within the microcavity, the anti-feedback threshold of the laser is further enhanced. This result represents a significant improvement 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] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0094] The above describes embodiments of the present disclosure. However, these embodiments are merely for illustrative purposes, and are not intended to limit the scope of the present disclosure. Although each embodiment is described above separately, this does not mean that the measures in each embodiment cannot be used advantageously in combination. The scope of the present disclosure is defined by the appended claims and their equivalents. Those skilled in the art can make various substitutions and modifications without departing from the scope of the present disclosure, and these substitutions and modifications should all fall within the scope of the present disclosure.

Claims

1. A coupled cavity semiconductor laser, characterized by, The application relates to a laser device. The laser device comprises: a whispering gallery microcavity for outputting a whispering gallery mode; a Fabry-Perot cavity, a first end of the Fabry-Perot cavity being connected with the whispering gallery microcavity; wherein a resonance mode of the Fabry-Perot cavity is coupled with the whispering gallery mode, and a light beam of the coupled mode is output from a second end of the Fabry-Perot cavity; the whispering gallery mode with a high quality factor is output through the whispering gallery microcavity, the resonance mode of the Fabry-Perot cavity is coupled, and then the coupled mode with a high Q value is output, so that the anti-feedback capability and the comprehensive output performance of the laser device are greatly improved; ， the light beam is transmitted along the whispering gallery microcavity to the Fabry-Perot cavity, a cross section of the whispering gallery microcavity is a hexagonal structure, the reflection spectrum envelope of the mode in the microcavity can be simplified when the cross section is a square, so that only the base mode and a group of high-order mode envelopes are present in the middle of two groups of adjacent longitudinal modes of the microcavity, the mode reflection rate is relatively high, and the mode in the microcavity is more pure, one group of parallel opposite sides in the hexagonal structure is parallel with a first diagonal line in the hexagonal structure, and the length m of the one group of parallel opposite sides is: wherein n is the length of the first diagonal line, the first diagonal line is parallel with the direction in which the light beam is transmitted in the Fabry-Perot cavity; the whispering gallery microcavity comprises: a rectangular hole arranged at a position with a high-order mode distribution intensity of the whispering gallery microcavity being high, for inhibiting the high-order mode of the whispering gallery microcavity; one group of opposite sides of the rectangular hole is perpendicular to the direction in which the light beam is transmitted in the Fabry-Perot cavity, the distance p between one side of the one group of opposite sides far 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; 2. The coupled cavity semiconductor laser of claim 1, wherein, the length v of the one group of opposite sides of the rectangular hole is 0.4d<=v<=2d, and the length w of the other group of opposite sides of the rectangular hole is v<=w<=3v, wherein d is the width of the Fabry-Perot cavity. The whispering gallery microcavity comprises an N-type limiting layer, an active layer and a P-type limiting layer which are sequentially stacked:

3. The coupled cavity semiconductor laser of claim 2, wherein, wherein the light beam is transmitted from the whispering gallery microcavity to the Fabry-Perot cavity along a direction parallel with the N-type limiting layer, the active layer and the P-type limiting layer which are sequentially stacked. Further comprising: an N-type substrate arranged on a surface of the N-type limiting layer far away from the active layer; an N-face electrode arranged on a surface of the N-type substrate far away from the N-type limiting layer; and an ohmic contact layer arranged on a surface of the whispering gallery microcavity far away from the N-type substrate and a surface of the Fabry-Perot cavity far away from the N-type substrate, wherein isolation grooves are arranged on the ohmic contact layer of the whispering gallery microcavity and the Fabry-Perot cavity; 4. The coupled cavity semiconductor laser of claim 3, wherein, a P-face electrode arranged on the ohmic contact layer.

5. The coupled cavity semiconductor laser of claim 3, wherein, The shape of the P-face electrode comprises a polygon, an arc-side polygon, a circular ring or a circle. The internal material of the rectangular hole is benzocyclobutene. The echo wall microcavity does not contain the P face electrode around and the Fabry-Perot cavity does not contain the P face electrode around is provided with benzocyclobutene, wherein the benzocyclobutene refractive index is less than the refractive index of the echo wall microcavity and the Fabry-Perot cavity material.

6. A test system for the coupled cavity semiconductor laser of any of claims 1-5, characterized in that, Comprise: DC bias; Laser, the first end of the laser is connected with the DC bias; The first end of the circulator is connected with the second end of the laser; The first end of the first optical splitter is connected with the second end of the circulator; The first end of the polarization controller is connected with the third end of the circulator; The first end of the optical attenuator is connected with the second end of the first optical splitter; The first end of the second optical splitter is connected with the second end of the optical attenuator, and the second end of the second optical splitter is connected with the second end of the polarization controller; The power meter is connected with the third end of the second optical splitter; The first end of the third optical splitter is connected with the third end of the first optical splitter; The optical spectrometer is connected with the second end of the third optical splitter; The first end of the photodetector is connected with the third end of the third optical splitter; The first end of the DC bias is connected with the second end of the photodetector; The first end of the electrical amplifier is connected with the second end of the DC bias; The frequency spectrometer is connected with the second end of the electrical amplifier; And The multimeter is connected with the third end of the DC bias.

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