Semiconductor laser for quantum gyroscope and preparation method thereof

Abstract

The application relates to the technical field of lasers, in particular to a semiconductor laser for a quantum gyroscope and a preparation method thereof. The semiconductor laser for the quantum gyroscope comprises a stacking structure, the stacking structure comprises an N-type substrate, an N-type cladding layer, an N-type waveguide layer, an active region, a first P-type waveguide layer and a waveguide structure which are stacked in a first direction in sequence, and the waveguide structure comprises a low-duty-cycle V-shaped groove grating, a multimode interference coupling beam splitting waveguide, a gain waveguide array, a multimode interference coupling beam combining waveguide, a high-duty-cycle V-shaped groove grating and a micro-tapered waveguide which are arranged and connected in a second direction in sequence. The application is favorable for realizing the semiconductor laser for the quantum gyroscope with high power and narrow linewidth under the premise of reducing the complexity of the device structure.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, and particularly relates to a semiconductor laser for quantum gyroscopes and its fabrication method. Background Technology

[0002] Inertial navigation systems occupy an extremely important position in modern technology and have gradually penetrated from aerospace and marine fields to intelligent vehicles. As its core sensor, the gyroscope plays a key role in achieving precise autonomous navigation. Currently, the most accurate gyroscope is the quantum gyroscope, also known as the atomic gyroscope. It is a new type of gyroscope based on atomic physics and quantum mechanics. Compared with traditional gyroscopes, it has significant advantages such as high sensitivity, low drift rate, and long lifespan, and has become a research hotspot and development direction in the field of inertial navigation.

[0003] Quantum gyroscopes require lasers for cooling, polarizing, and signal detection of atoms, placing demands on lasers with "narrow linewidth" and "high power." Regarding narrow linewidth, taking rubidium atoms as an example, their atomic transition linewidth is ≤6MHz. A narrow linewidth laser means that the energy of the output spectrum is concentrated in a narrower frequency range, allowing for strict matching with the atomic absorption spectrum. This reduces the excitation of non-target energy levels, improves the efficiency and effectiveness of atomic manipulation, and ultimately enhances the signal-to-noise ratio. Therefore, the laser linewidth must be strictly controlled within the natural linewidth of atomic transitions, preferably below 5MHz. As for high power, the specific requirements are as follows: Taking an atomic interferometer gyroscope as an example, during the laser cooling and confinement stage, the number of atoms decreases due to diffusion and collisions with the cavity walls. The detection stage requires a sufficient atomic population to enhance the interference signal, improve the signal-to-noise ratio, and increase measurement accuracy and sensitivity. Therefore, the output power is typically required to be in the hundreds of mW range. Research by the French III-V laboratory indicates that approximately 500mW of laser power can meet the requirements of an atomic interferometer gyroscope. Among the many types of light sources, semiconductor lasers have become the mainstream light source choice for atomic gyroscopes due to their unique advantages such as narrow linewidth, high power, chip-level operation, and high reliability.

[0004] To meet the demand for narrow-linewidth (≤5MHz) laser output, most domestic and international institutions use buried gratings or surface gratings for longitudinal mode screening to achieve the narrow-linewidth effect. To meet the high-power (≥500mW) requirement, research institutions both domestically and internationally generally adopt external cavity solutions for narrow-linewidth seed source integrated optical amplifiers, such as hybrid integration methods like Master Oscillator Power Amplifier (MOPA). However, these solutions are structurally complex, have poor stability, and are subject to single-chip embargoes. Furthermore, single-chip solutions suffer from low power; for example, the distributed feedback lasers provided by related technologies have a power of approximately 180mW, which is clearly insufficient to meet the power requirements of quantum gyroscopes. Therefore, there is an urgent need to develop high-performance monolithically integrated lasers for atomic gyroscopes to meet the development needs of quantum gyroscope technology. Summary of the Invention

[0005] In view of this, the present invention aims to provide a semiconductor laser for quantum gyroscopes and a method for fabricating the same, which is beneficial to realize a high-power, narrow-linewidth semiconductor laser for quantum gyroscopes while reducing the complexity of the device structure.

[0006] To achieve the above objectives, the technical solution created by this invention is implemented as follows:

[0007] This invention provides a semiconductor laser for quantum gyroscopes, comprising: a stacked structure, the stacked structure including an N-type substrate, an N-type cladding, an N-type waveguide layer, an active region, a first P-type waveguide layer, and a waveguide structure stacked sequentially along a first direction, the waveguide structure including a low duty cycle V-groove grating, a multimode interference coupled beam splitter waveguide, a gain waveguide array, a multimode interference coupled beam combiner waveguide, a high duty cycle V-groove grating, and a microconical waveguide arranged sequentially and connected along a second direction.

[0008] Furthermore, the period of the low duty cycle V-groove grating is the same as that of the high duty cycle V-groove grating, but the duty cycle of the low duty cycle V-groove grating is lower than that of the high duty cycle V-groove grating.

[0009] Furthermore, the low duty cycle V-groove grating includes a plurality of first grating pillars spaced apart along the second direction, the size of each first grating pillar gradually increasing from the top to the bottom of the first grating pillar in the second direction; the high duty cycle V-groove grating includes a plurality of second grating pillars spaced apart along the second direction, the size of each second grating pillar gradually increasing from the top to the bottom of the second grating pillar in the second direction.

[0010] Furthermore, in the third direction, the dimensions of the low duty cycle V-groove grating are the same as those of the high duty cycle V-groove grating.

[0011] Furthermore, the gain waveguide array includes multiple strip waveguides spaced apart along a third direction, each strip waveguide having the same shape and extending along a second direction.

[0012] Furthermore, the waveguide structure is formed by etching a second P-type waveguide layer, a P-type cladding layer, and a P-type capping layer stacked along the first direction.

[0013] Furthermore, the microconical waveguide is a strip-shaped conical waveguide extending along the second direction. The microconical waveguide has a first end and a second end arranged along the second direction. The first end is connected to a high duty cycle V-groove grating. The size of the microconical waveguide in the third direction gradually increases from the first end to the second end.

[0014] Furthermore, in the third direction, the size of the low duty cycle V-groove grating is in the range of 3.9μm to 4.1μm, the size of the multimode interference coupled beam splitter waveguide is in the range of 30μm to 50μm, the size of the multimode interference coupled beam combiner waveguide is in the range of 30μm to 50μm, the size of the high duty cycle V-groove grating is in the range of 3.9μm to 4.1μm, and the maximum size of the microconical waveguide is in the range of 14μm to 16μm.

[0015] Another aspect of this invention provides a method for fabricating a semiconductor laser for quantum gyroscopes. The method includes: forming an initial stacked structure, comprising an N-type substrate, an N-type cladding, an N-type waveguide layer, an active region, a first P-type waveguide layer, and an initial waveguide structure stacked sequentially along a first direction; etching the initial waveguide structure to form a waveguide structure, the waveguide structure comprising a low duty cycle V-groove grating, a multimode interference coupled beam splitter waveguide, a gain waveguide array, a multimode interference coupled beam combiner waveguide, a high duty cycle V-groove grating, and a microconical waveguide arranged sequentially and connected along a second direction.

[0016] Furthermore, forming a low duty cycle V-groove grating and forming a high duty cycle V-groove grating includes: forming a mask layer on top of a portion of the initial waveguide structure for which the low duty cycle V-groove grating and the high duty cycle V-groove grating are subsequently formed; the mask layer includes a plurality of mask blocks spaced apart along a second direction; each mask block includes a stacked first portion and a second portion; the first portion and the second portion have the same dimensions in a third direction; the first portion has a larger dimension in the second direction than the second portion in the second direction; the first portion is located below the second portion; and in the first direction, the first portion is directly opposite the second portion; and the portion of the initial waveguide structure is etched using the mask layer as a mask to obtain the low duty cycle V-groove grating and the high duty cycle V-groove grating.

[0017] Compared with existing technologies, this invention achieves the following beneficial effects: Addressing the problem that monolithic integrated semiconductor lasers for quantum gyroscopes struggle to simultaneously achieve high power and narrow linewidth, this invention provides a semiconductor laser for quantum gyroscopes. In the waveguide structure of this quantum gyroscope, two V-groove gratings with the same period but different duty cycles are used to construct an overlapping reflection spectrum with a shifted center wavelength, obtaining a single-frequency laser in the MHz range. The use of V-groove gratings reduces losses, thereby increasing power. Furthermore, to ensure higher power under single-mode conditions, multimode interference-coupled beam-combining and multimode interference-coupled beam-splitting waveguides are used to coherently combine multiple single-frequency laser beams, obtaining a single-frequency seed light greater than 200mW. Based on this, an on-chip micro-conical waveguide is integrated to amplify the single-frequency laser a second time to achieve high power, ultimately realizing a high-power, narrow-linewidth, single-chip semiconductor laser for quantum gyroscopes.

[0018] This invention can form a mask block that is narrow at the top and wide at the bottom using a conventional lithography machine. Based on a specially designed mask block, a low duty cycle V-groove grating and a high duty cycle V-groove grating can be formed using a conventional etching process. This avoids the need to use a more expensive stepper lithography machine to form V-groove gratings, and helps to reduce the difficulty and cost of fabricating V-groove gratings (both low duty cycle and high duty cycle V-groove gratings). Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0020] Figure 1 A three-dimensional structural schematic diagram of a semiconductor laser for quantum gyroscopes as described in an embodiment of the present invention;

[0021] Figure 2 A side view of the structure during the fabrication process of the semiconductor laser for quantum gyroscopes as described in the embodiment of the present invention;

[0022] Figure 3 A side view of a semiconductor laser oriented towards a quantum gyroscope, as described in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0025] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] refer to Figures 1 to 3 The present invention provides a semiconductor laser for quantum gyroscopes, comprising: a stacked structure, the stacked structure including an N-type substrate 201, an N-type cladding 202, an N-type waveguide layer 203, an active region 204, a first P-type waveguide layer and a waveguide structure stacked sequentially along a first direction Z; the waveguide structure including a low duty cycle V-groove grating 101, a multimode interference coupling beam splitter waveguide 102, a gain waveguide array 103, a multimode interference coupling beam combiner waveguide 104, a high duty cycle V-groove grating 105 and a microconical waveguide 106 arranged sequentially and connected along a second direction X.

[0029] In the semiconductor laser for quantum gyroscopes provided by this invention, a low-power, high-coherence seed laser is split into multiple lasers via a multimode interference-coupled beam-splitting waveguide 102, based on the self-image principle. Each laser has the same frequency, linewidth, and phase difference. The low-power, high-coherence seed laser is filtered by a low-duty-cycle V-groove grating and a high-duty-cycle V-groove grating, removing longitudinal modes that do not meet the Bragg condition and leaving only the low-power single-mode laser formed by the longitudinal mode with the lowest loss. Each laser beam is independently amplified in multiple gain channels separated by the gain waveguide array 103, thereby avoiding the thermal effects / nonlinear limitations of single channels. Finally, the amplified multi-laser beams are synchronously recombined into a single laser beam through the multimode interference coupling beam combiner waveguide 104, achieving power superposition and maintaining single-mode characteristics. The low duty cycle V-groove grating 101 and the high duty cycle V-groove grating 105 distributed at both ends utilize the reflection spectrum overlap to narrow the linewidth, lock the frequency, and reduce losses. Finally, the beams are gradually amplified through the microconical waveguide 106 to suppress higher-order modes, ultimately outputting a high-power single-mode laser.

[0030] Among them, the high duty cycle V-groove grating 105 and the low duty cycle V-groove grating 101 are both Bragg gratings.

[0031] Furthermore, the period of the low duty cycle V-groove grating 101 is the same as that of the high duty cycle V-groove grating 105, but the duty cycle of the low duty cycle V-groove grating 101 is lower than that of the high duty cycle V-groove grating 105.

[0032] In some embodiments, the duty cycle of the low duty cycle V-groove grating 101 is in the range of 0.05 to 0.45, preferably 0.2; the duty cycle of the high duty cycle V-groove grating 105 is in the range of 0.55 to 0.95, preferably 0.8; the difference between the duty cycle of the low duty cycle V-groove grating 101 and the duty cycle of the high duty cycle V-groove grating 105 is in the range of 0.1 to 0.9, preferably 0.6.

[0033] In some embodiments, the period of the low duty cycle V-groove grating 101 or the period of the high duty cycle V-groove grating 105 is in the range of 10 to 100.

[0034] The offset between the center wavelength of the reflection spectrum of the low duty cycle V-groove grating 101 and the center wavelength of the reflection spectrum of the high duty cycle V-groove grating 105 is in the range of 0.1nm to 0.5nm. The reflection spectrum of the low duty cycle V-groove grating 101 and the reflection spectrum of the high duty cycle V-groove grating 105 overlap to form an extremely narrow reflection spectrum, so as to effectively narrow the linewidth and lock the frequency, thereby realizing single-frequency laser output in the 779.5nm to 780.5nm band.

[0035] Furthermore, the low duty cycle V-groove grating 101 includes a plurality of first grating pillars spaced apart along the second direction X, the size of each first grating pillar gradually increasing from the top to the bottom of the first grating pillar in the second direction X; the high duty cycle V-groove grating 105 includes a plurality of second grating pillars spaced apart along the second direction X, the size of each second grating pillar gradually increasing from the top to the bottom of the second grating pillar in the second direction X.

[0036] It should be noted that the first and second grating pillars are exactly the same size.

[0037] In some embodiments, in the second direction X, the top dimension of the second grating post is in the range of 1.5 μm to 10 μm, and the bottom dimension of the second grating post is in the range of 2.5 μm to 11 μm.

[0038] This invention employs a V-groove grating, solving the problem of high loss in traditional rectangular groove gratings. Furthermore, based on the coupled-mode equation and scattering matrix theory, by utilizing two sets of V-groove gratings with the same period but different duty cycles, two reflection spectra with a slight shift in center wavelength can be generated, thereby obtaining a single-frequency laser with narrower linewidth. For the multimode interference coupled beam splitter waveguide 102 and the multimode interference coupled beam combiner waveguide 104, the influencing factors of effective refractive index modulation can be analyzed based on the self-imaging principle and the photon / carrier rate equation. By optimizing the physical structural parameters of the multimode interference coupled beam splitter waveguide 102 and the multimode interference coupled beam combiner waveguide 104, efficient transmission and coherent combining of single-frequency light waves can be achieved. Finally, by integrating a micro-conical waveguide 106, the single-frequency laser is amplified a second time while maintaining single-mode operation, achieving high-power output.

[0039] Furthermore, in the third direction Y, the dimensions of the low duty cycle V-groove grating 101 are the same as those of the high duty cycle V-groove grating 105.

[0040] In some embodiments, the dimensions of the low duty cycle V-groove grating 101 and the high duty cycle V-groove grating 105 are in the range of 3.9 μm to 4.1 μm, so as to utilize narrow ridge waveguides to confine the optical field.

[0041] Furthermore, the gain waveguide array 103 includes multiple strip waveguides spaced apart along the third direction Y, each strip waveguide having the same shape and each strip waveguide extending along the second direction X.

[0042] In some embodiments, the number of strip waveguides in the gain waveguide array 103 is in the range of 3 to 6. In some examples, the gain waveguide array 103 includes 4 strip waveguides spaced Y-spaced along a third direction.

[0043] It should be noted that the first direction, the second direction, and the third direction are perpendicular to each other.

[0044] Furthermore, the waveguide structure is formed by etching a second P-type waveguide layer, a P-type cladding layer 206, and a P-type capping layer 207 stacked along the first direction Z. The second P-type waveguide layer and the first P-type waveguide layer are integrally formed structures, and the second P-type waveguide layer and the first P-type waveguide layer together constitute the P-type waveguide layer 205.

[0045] Furthermore, the micro-conical waveguide 106 is a strip-shaped conical waveguide extending along the second direction X. The micro-conical waveguide 106 has a first end and a second end arranged along the second direction X. The first end is connected to the high duty cycle V-groove grating 105. The size of the micro-conical waveguide 106 in the third direction Y gradually increases from the first end to the second end.

[0046] In some embodiments, in the third direction Y, the size of the second end of the microtapered waveguide 106 is in the range of 12μm to 16μm, and the size of the first end of the microtapered waveguide 106 is in the range of 4μm to 6μm. In the second direction X, the length of the microtapered waveguide 106 is in the range of 1mm to 2mm. The structural design of the microtapered waveguide can ensure that the output laser is coupled into the single-mode fiber (single-mode fiber with a core diameter in the range of 8μm to 10μm) more efficiently.

[0047] Furthermore, the central axes of the low duty cycle V-groove grating 101 extending along the second direction X, the central axes of the multimode interference coupled beam splitter waveguide 102 extending along the second direction X, the central axes of the gain waveguide array 103 extending along the second direction X, the central axes of the multimode interference coupled beam combiner waveguide 104 extending along the second direction X, the central axes of the high duty cycle V-groove grating 105 extending along the second direction X, and the central axes of the microconical waveguide 106 extending along the second direction X all coincide with each other.

[0048] Furthermore, in the third direction Y, the dimensions of the low duty cycle V-groove grating 101 are in the range of 3.9 μm to 4.1 μm, the dimensions of the multimode interference coupled beam splitter waveguide 102 are in the range of 30 μm to 50 μm, the dimensions of the multimode interference coupled beam combiner waveguide 104 are in the range of 30 μm to 50 μm, the dimensions of the high duty cycle V-groove grating 105 are in the range of 3.9 μm to 4.1 μm, and the maximum dimension of the microconical waveguide 106 is in the range of 14 μm to 16 μm.

[0049] In some examples, the size of the low duty cycle V-groove grating 101 is 4 micrometers in the third direction Y, and the size of the high duty cycle V-groove grating 105 is 4 micrometers.

[0050] In some embodiments, the semiconductor laser for quantum gyroscopes further includes a P electrode and an N electrode. The N electrode is located on the surface of the N-type substrate 201 away from the N-type cladding 202, and the P electrode is located on the top surface of the waveguide structure. The P electrode and the N electrode are used to connect to external circuitry to achieve electrical injection. Both the P electrode and the N electrode are metal electrodes.

[0051] In some embodiments, the P electrode is located at the top of the multimode interference coupled beam splitter waveguide 102, the top of the gain waveguide array 103, the top of the multimode interference coupled beam combiner waveguide 104, and the top of the microconical waveguide 106.

[0052] In some embodiments, the stacked structure of semiconductor lasers for quantum gyroscopes can be a GaAs-based edge-emitting semiconductor laser chip.

[0053] In some embodiments, the end of the stacked structure away from the microconical waveguide 106 has a high-reflection film, and the end of the stacked structure away from the high-reflection film is the light-emitting cavity surface, which has an anti-reflection film.

[0054] The semiconductor laser for quantum gyroscopes provided by this invention splits single-frequency light, after frequency selection by a low-duty-cycle V-groove grating 101 and a high-duty-cycle V-groove grating 105, into multiple single-frequency beams by a multimode interference-coupled beam-splitting waveguide 102. Each single-frequency beam is injected into a corresponding channel formed by a strip waveguide in a gain waveguide array 103 for independent amplification. The beam-splitting process of the multimode interference-coupled beam-splitting waveguide 102 is based on the self-imaging principle. By optimizing the refractive index distribution and physical structural parameters of the waveguide sidewalls, lossless light transmission is ensured. In the gain waveguide array 103, phase synchronization of the light waves in each channel is achieved through carrier concentration modulation and rate equation theory, providing a basis for subsequent... The coherent beam combining lays the foundation; multiple single-frequency beams are re-superimposed in the multimode interference coupling beam combining waveguide 104 through the multimode interference effect, and the laser power after coherent combining is increased while maintaining the narrow linewidth characteristic. Thus, a narrow linewidth seed beam is formed. The narrow linewidth seed beam enters the microconical waveguide 106, and the gain medium volume is increased by gradually expanding the waveguide cross section, further amplifying the power to ≥500mW. The microconical structure design of the microconical waveguide 106 can suppress the high-order mode self-excitation caused by edge carrier aggregation and maintain single-mode output. The microconical waveguide 106 optimizes the transmission characteristics through the beam propagation method, and finally outputs high beam quality laser at the end face.

[0055] Another aspect of this invention provides a method for fabricating a semiconductor laser for quantum gyroscopes. The method includes: forming an initial stacked structure comprising an N-type substrate 201, an N-type cladding 202, an N-type waveguide layer 203, an active region 204, a first P-type waveguide layer, and an initial waveguide structure stacked sequentially along a first direction Z; etching the initial waveguide structure to form a waveguide structure comprising a low duty cycle V-groove grating 101, a multimode interference-coupled beam splitter waveguide 102, a gain waveguide array 103, a multimode interference-coupled beam combiner waveguide 104, a high duty cycle V-groove grating 105, and a microconical waveguide 106 arranged sequentially and connected along a second direction X.

[0056] In some embodiments, the initial waveguide structure includes a second P-type waveguide layer, a P-type cladding 206, and a P-type capping layer 207 stacked along a first direction.

[0057] In some embodiments, the specific steps for forming the low duty cycle V-groove grating 101 and the high duty cycle V-groove grating 105 are as follows: First, a mask layer is formed on top of the initial waveguide structure for which the low duty cycle V-groove grating 101 and the high duty cycle V-groove grating 105 are subsequently formed using a photolithography process. The mask layer includes a plurality of mask blocks 208 arranged at intervals along the second direction X. Each mask block 208 includes a stacked first part and a second part. The first part and the second part have the same dimensions in the third direction Y. The first part has a larger dimension in the second direction X than the second part in the second direction X. The first part is located below the second part and is directly opposite the second part in the first direction Z. Thus, by using the mask layer including the mask blocks 208 as a mask to etch the initial waveguide structure, the low duty cycle V-groove grating 101 and the high duty cycle V-groove grating 105 can be obtained, i.e., a V-groove grating is fabricated. The V-groove grating is beneficial for solving the problem of high loss in traditional rectangular groove gratings.

[0058] In some embodiments, waveguide structures can be formed using methods such as plasma-enhanced chemical vapor deposition, photolithography, and plasma etching.

[0059] In some embodiments, after forming the stacked structure, the method for fabricating a semiconductor laser facing a quantum gyroscope further includes forming a P electrode at a corresponding position on the top surface of the stacked structure and forming an N electrode at a corresponding position on the bottom surface of the stacked structure.

[0060] In some embodiments, the method for fabricating a semiconductor laser for a quantum gyroscope further includes: depositing an antireflection film on the light-emitting cavity surface of the device, and depositing a high-reflection film on the other end cavity surface opposite to the light-emitting cavity surface.

[0061] To address the problems of complex structure, poor stability, and susceptibility to environmental disturbances leading to reduced detection accuracy and sensitivity in hybrid integrated semiconductor lasers, this invention provides a semiconductor laser for quantum gyroscopes and its fabrication method. The semiconductor laser for quantum gyroscopes uses two sets of V-groove gratings with different duty cycles for longitudinal mode selection, effectively compressing the linewidth while achieving greater frequency stability. Furthermore, by integrating multimode interference coupling waveguides, gain arrays, and microconical amplifiers on-chip, it maintains narrow linewidth characteristics while achieving better amplification power compared to traditional hybrid integrated solutions, effectively reducing system size and better aligning with the mainstream trend of chip-based miniaturization.

[0062] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0063] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A semiconductor laser for quantum gyroscopes, characterized in that, include: A stacked structure, comprising an N-type substrate, an N-type cladding, an N-type waveguide layer, an active region, a first P-type waveguide layer, and a waveguide structure stacked sequentially along a first direction, wherein the waveguide structure comprises a low duty cycle V-groove grating, a multimode interference coupled beam splitter waveguide, a gain waveguide array, a multimode interference coupled beam combiner waveguide, a high duty cycle V-groove grating, and a microconical waveguide arranged sequentially and connected along a second direction; The period of the low duty cycle V-groove grating is the same as that of the high duty cycle V-groove grating; the duty cycle of the low duty cycle V-groove grating is in the range of 0.05 to 0.45; the duty cycle of the high duty cycle V-groove grating is in the range of 0.55 to 0.

95. The low duty cycle V-groove grating includes a plurality of first grating pillars spaced apart along a second direction, wherein the size of each first grating pillar in the second direction gradually increases from the top to the bottom of the first grating pillar. The high duty cycle V-groove grating includes a plurality of second grating pillars spaced apart along a second direction, wherein the size of each second grating pillar in the second direction gradually increases from the top to the bottom of the second grating pillar. In the third direction, the size of the second end of the microconical waveguide is in the range of 12μm to 16μm, and the size of the first end of the microconical waveguide is in the range of 4μm to 6μm. The first direction, the second direction, and the third direction are perpendicular to each other.

2. The semiconductor laser for quantum gyroscopes according to claim 1, characterized in that, In the third direction, the dimensions of the low duty cycle V-groove grating are the same as those of the high duty cycle V-groove grating.

3. The semiconductor laser for quantum gyroscopes according to claim 1, characterized in that, The gain waveguide array includes multiple strip waveguides spaced apart along a third direction, each strip waveguide having the same shape and extending along a second direction.

4. The semiconductor laser for quantum gyroscopes according to claim 1, characterized in that, The waveguide structure is formed by etching a second P-type waveguide layer, a P-type cladding layer, and a P-type capping layer stacked along a first direction.

5. The semiconductor laser for quantum gyroscopes according to claim 1, characterized in that, The microconical waveguide is a strip-shaped conical waveguide extending along the second direction. The microconical waveguide has a first end and a second end arranged along the second direction. The first end is connected to the high duty cycle V-groove grating. The size of the microconical waveguide in the third direction gradually increases from the first end to the second end.

6. The semiconductor laser for quantum gyroscopes according to claim 5, characterized in that, In the third direction, the size of the low duty cycle V-groove grating is in the range of 3.9μm to 4.1μm, the size of the multimode interference coupling beam splitter waveguide is in the range of 30μm to 50μm, the size of the multimode interference coupling beam combiner waveguide is in the range of 30μm to 50μm, the size of the high duty cycle V-groove grating is in the range of 3.9μm to 4.1μm, and the maximum size of the microconical waveguide is in the range of 14μm to 16μm.

7. A method for fabricating a semiconductor laser for quantum gyroscopes, characterized in that, A method for fabricating a semiconductor laser oriented towards a quantum gyroscope, as described in any one of claims 1 to 6, comprises: An initial stacked structure is formed, the initial stacked structure comprising an N-type substrate, an N-type cladding, an N-type waveguide layer, an active region, a first P-type waveguide layer, and an initial waveguide structure stacked sequentially along a first direction; The initial waveguide structure is etched to form a waveguide structure, which includes a low duty cycle V-groove grating, a multimode interference coupled beam splitter waveguide, a gain waveguide array, a multimode interference coupled beam combiner waveguide, a high duty cycle V-groove grating, and a microconical waveguide arranged sequentially and connected along a second direction.

8. The method for fabricating a semiconductor laser for a quantum gyroscope according to claim 7, characterized in that, Forming a low duty cycle V-groove grating and forming a high duty cycle V-groove grating include: A mask layer is formed on top of the initial waveguide structure for forming low duty cycle V-groove gratings and high duty cycle V-groove gratings. The mask layer includes a plurality of mask blocks spaced apart along a second direction. Each mask block includes a stacked first part and a second part. The first part and the second part have the same dimensions in a third direction. The first part has a larger dimension in the second direction than the second part in the second direction. The first part is located below the second part and is directly opposite the second part in the first direction. Using the mask layer as a mask, a portion of the initial waveguide structure is etched to obtain low duty cycle V-groove gratings and high duty cycle V-groove gratings.

Images