A semiconductor laser with a hybrid integrated ridge waveguide structure and a method of manufacturing the same

Abstract

The application relates to the technical field of semiconductor lasers, in particular to a semiconductor laser with a mixed integrated ridge waveguide structure and a preparation method thereof. A deep groove structure is arranged at the output end of the ridge waveguide, a nonlinear saturated absorption material is filled in the groove, and the deep groove structure is distributed in an H shape along the cavity length direction of the ridge waveguide, that is, the middle part of the deep groove structure is thin, and the two sides are thick. The application utilizes the light intensity dependent absorption characteristics of the saturated absorption material, forms strong absorption on high-order modes with energy concentrated on the two sides of the ridge, maintains low-loss transmission on the central fundamental mode, greatly widens the mode loss difference, and significantly improves the purity of the fundamental mode and the light spot quality; the preparation process is compatible with existing production equipment, high-efficiency batch preparation can be realized, and the application is suitable for high light beam quality demand scenes such as optical communication and laser precision machining.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, and more specifically to a semiconductor laser with a hybrid integrated ridge waveguide structure and its fabrication method. Background Technology

[0002] Semiconductor lasers are core components of various optoelectronic devices. Among them, ridge waveguide edge-emitting semiconductor lasers are the mainstream devices for current industrial applications due to their advantages of simple structure, mature fabrication process, and ease of mass production. Traditional ridge waveguides rely on the lateral refractive index difference introduced by etching to achieve optical field confinement. Their single transverse mode operation parameter window is relatively narrow, and the precision requirements for structural dimensions such as ridge waveguide width, etching depth, and epitaxial layer thickness are extremely stringent.

[0003] During mass production, constraints such as lithography alignment deviations, etching rate uniformity fluctuations, and epitaxial growth film thickness tolerances can lead to the excitation of higher-order transverse modes within the resonant cavity, resulting in multi-mode lasing, if the stability and precision of the processing technology are insufficient. The interference and superposition of these multi-mode optical fields during far-field propagation cause a non-Gaussian beam distribution, leading to side lobes, beam splitting, and ultimately a significant decrease in beam quality, failing to meet the performance requirements of high-end applications. Therefore, achieving efficient higher-order mode suppression based on ridge waveguide structures while simultaneously improving the device's tolerance to process fluctuations and ensuring mass production yield and device efficiency is a pressing technical challenge in this field.

[0004] To address the issues of easy lasing of higher-order transverse modes and poor beam quality in ridge waveguide lasers, patent CN111641104A discloses a semiconductor laser that optimizes transverse mode characteristics by setting multiple sets of separate current injection electrodes to control the intracavity optical field distribution. However, this approach requires precise alignment of each separate electrode with the underlying current injection layer, significantly increasing the complexity and alignment difficulty of the photolithography process. Simultaneously, the transverse diffusion effect of the current expands the heat-affected zone. Increasing the electrode spacing to achieve mode control would significantly reduce the current injection efficiency, degrading the electro-optical conversion efficiency of the device, resulting in limited overall performance gains. Patent CN113937616A discloses a ridge waveguide semiconductor laser that uses a grating structure with a specific morphology etched on the ridge waveguide to select specific transverse modes through the grating's mode selection effect. However, this approach requires extremely high control over the small-period grating, including etching depth, sidewall perpendicularity, and period uniformity, greatly increasing the risk of short circuits and making it unsuitable for mass production. Summary of the Invention

[0005] To address the issues that traditional ridge waveguide-side-emitting semiconductor lasers have narrow single-transverse mode operating parameter windows, are prone to beam quality degradation due to process deviations in exciting higher-order transverse modes, and that existing transverse mode optimization schemes generally suffer from high process complexity, significant device efficiency loss, and incompatibility with large-scale mass production, this invention provides a semiconductor laser with a hybrid integrated ridge waveguide structure and its fabrication method.

[0006] The technical solution of this invention is as follows: In a first aspect, the present invention provides a semiconductor laser with a hybrid integrated ridge waveguide structure, comprising, from bottom to top, a substrate and a stacked structure. The upper surface of the stacked structure has two parallel grooves, and the region between the two grooves forms a ridge waveguide extending along the cavity length direction. The outer regions of the two grooves form shoulders. A deep groove structure is provided at the output end of the ridge waveguide. The deep groove structure is distributed in an "H" shape along the cavity length direction of the ridge waveguide, that is, the deep groove structure is thin in the middle and thick on both sides along the cavity length direction of the ridge waveguide. The deep groove structure is filled with a nonlinear saturable absorption material.

[0007] Furthermore, the width of the deep groove structure and the width of the ridge waveguide are both 1.2~15μm.

[0008] Furthermore, the length of the ridge waveguide is the same as the cavity length of a single semiconductor laser tube, and the height of the ridge waveguide is 0.1~5μm.

[0009] Furthermore, the depth of the deep groove structure is 0.2~3μm.

[0010] Furthermore, along the cavity length direction of the ridge waveguide, the lengths of the two sides of the deep groove structure are 2~50μm, and the length of the middle part of the deep groove structure is 0.2~45μm; and the lengths of the two sides of the deep groove structure are greater than the length of the middle part of the deep groove structure.

[0011] Furthermore, the substrate of the nonlinear saturable absorbing material is yttrium aluminum garnet (YAG) or spinel, and the doping elements are Cr, V or Co. The absorption coefficient of the material decreases with the increase of incident light intensity. At the same time, the material thickness in the deep groove is thinner than the light intensity at the center of the fundamental mode, which triggers the saturable absorption characteristics of the material and realizes low-loss transmission. There are strong light fields on both sides of the ridge waveguide for higher-order modes. At this time, the material thickness at the edge position is large, which cannot meet the transmission window for saturable absorption. It is a strong absorbing material and can strongly absorb the light field of higher-order modes. This realizes the filtering effect of higher-order light fields in the ridge waveguide laser.

[0012] Furthermore, the doping concentration of the dopant element is 0.1 at.% to 5 at.%, where at.% represents the atomic content percentage.

[0013] Furthermore, the stacked structure comprises, from bottom to top, an N-confining layer, an N-waveguide layer, a quantum well active layer, a P-waveguide layer, and a P-confining layer; the bottom of the deep trench structure is in contact with the upper surface of the quantum well active layer.

[0014] Furthermore, the upper surface of the ridge waveguide is covered with an ohmic contact layer, and the stacked structure outside the ridge waveguide region is covered with an insulating layer. The ohmic contact layer and the insulating layer are covered with a P-plane metal layer. The insulating layer is made of any one of SiO2, Si3N4, or AlN. The P-plane metal layer is made of at least two of titanium, platinum, gold, nickel, germanium, chromium, and tin.

[0015] In a second aspect, the present invention provides a method for fabricating the above-mentioned semiconductor laser having a hybrid integrated ridge waveguide structure, comprising the following steps: S1. Select a substrate and use metal-organic chemical vapor deposition to grow a stacked structure and an ohmic contact layer on the substrate in sequence to obtain a laser epitaxial wafer. S2. Ridge waveguides are formed on the epitaxial wafer of a laser using photolithography and etching techniques; S3. Photolithographic etching is performed in the output region of the ridge waveguide to form a deep trench structure; S4. Deposit a layer of nonlinear saturated absorber material within the deep trench structure; S5. Subsequently, an insulating layer is deposited on the surface of the region outside the ridge waveguide of the laser epitaxial wafer; S6. Subsequently, a P-plane metal layer is deposited on the surface of the laser epitaxial wafer, and an N-plane metal layer is deposited on the back side of the substrate. After cleaving and coating, a semiconductor laser is obtained.

[0016] The beneficial effects of this invention are as follows: The semiconductor laser with a hybrid integrated ridge waveguide structure provided by this invention integrates a nonlinear absorbing material with a thin center and thick sides at the output end of the ridge waveguide structure. By utilizing the difference in optical field energy distribution between the fundamental transverse mode and higher-order transverse modes in the waveguide, combined with the saturable absorption characteristics of the material, the fundamental transverse mode with concentrated central light intensity is triggered to achieve saturable absorption in the thin material region, thus achieving low-loss transmission. Meanwhile, the higher-order transverse modes with stronger lateral light intensity are in a strong absorption state in the thick material region and are filtered out by loss. Without introducing complex processes or significantly increasing the additional losses of the device, this invention effectively widens the parameter window for single-transverse mode operation of the ridge waveguide, improves the device's tolerance to process fluctuations, and significantly improves the purity of the fundamental mode output and the quality of the far-field beam. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a partial structural schematic diagram of a semiconductor laser with a hybrid integrated ridge waveguide structure provided by the present invention.

[0019] Figure 2 This is a schematic diagram of the overall structure of a semiconductor laser with a hybrid integrated ridge waveguide structure provided by the present invention.

[0020] Figure 3 This is a far-field beam pattern of the TE0 fundamental mode propagating outside a semiconductor laser with a hybrid integrated ridge waveguide structure in Example 1.

[0021] Figure 4 This is a far-field beam pattern of the TE1 higher-order mode propagating outside a semiconductor laser with a hybrid integrated ridge waveguide structure in Example 1.

[0022] Figure 5 The diagram shows the transmission of the TE0 fundamental mode in Example 1 within the hybrid integrated ridge waveguide structure of a semiconductor laser with a hybrid integrated ridge waveguide structure. In the diagram, the arrows indicate the positions of the nonlinear saturable absorber material.

[0023] Figure 6 The diagram shows the transmission of the TE1 higher-order mode in Example 1 within the hybrid integrated ridge waveguide structure of a semiconductor laser with a hybrid integrated ridge waveguide structure. In the diagram, the arrows indicate the positions of the nonlinear saturable absorber material.

[0024] Figure 7 This is a graph showing the transmittance characteristics of a nonlinear saturated absorber.

[0025] In the figure, 1-substrate, 2-N confinement layer, 3-N waveguide layer, 4-quantum well active layer, 5-P waveguide layer, 6-P confinement layer, 7-ridge waveguide, 8-ohmic contact layer, 9-P-plane metal layer, 10-groove, 11-shoulder, 12-insulating layer, 13-nonlinear saturable absorber material. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0027] Example 1 A semiconductor laser with a hybrid integrated ridge waveguide structure, such as Figures 1-2 As shown, from bottom to top, the structure includes a substrate 1, an N-confinement layer 2, an N-waveguide layer 3, a quantum well active layer 4, a P-waveguide layer 5, and a P-confinement layer 6. The upper surface of the P-confinement layer 6 has two parallel grooves 10. The region between the two grooves 10 forms a ridge waveguide 7 extending along the cavity length direction. The outer regions of the two grooves 10 form shoulders 11. A deep trench structure is provided at the output end of the ridge waveguide 7. The width of the deep trench structure and the width of the ridge waveguide 7 are both 1.2 μm. The height of the ridge waveguide 7 is 3 μm, and the depth of the deep trench structure is 2.1 μm. The deep trench structure is H-shaped along the cavity length direction of the ridge waveguide. The distribution includes two side regions within 0.4 μm of each side edge of the deep trench structure, each with a length of 10 μm along the cavity length direction. The middle region, located between the two side regions, has a length of 3 μm. The middle region is interconnected with the two side regions, together forming an "H"-shaped deep trench structure. The deep trench structure is filled with a nonlinear saturated absorber material 13. The upper surface of the ridge waveguide 7 is covered with an ohmic contact layer 8. An insulating layer 12 is covered on the P-confining layer 6 outside the ridge waveguide 7 region. A P-plane metal layer 9 is covered on top of the ohmic contact layer 8 and the insulating layer 12. An N-plane metal layer is covered on the back side of the substrate 1.

[0028] The nonlinear saturated absorber 13 has a YAG substrate, is doped with Cr, and has a doping concentration of 0.5 at.%. The substrate 1 is a GaAs wafer with a crystal orientation of (100) and a thickness of 500 μm; the N-confinement layer 2 is made of AlGaAs and has a thickness of 1 μm; the N-waveguide layer 3 is made of AlGaAs and has a thickness of 1 μm; the quantum well active layer 4 is composed of GaInP, AlGaInP, and GaInP layers stacked from bottom to top, with a thickness of 40 nm; the P-confinement layer 6 is made of AlGaAs and has a thickness of 1 μm; the P-waveguide layer 5 is made of AlGaAs and has a thickness of 1 μm; the insulating layer 12 is made of SiO2 and has a thickness of 200 nm; the P-plane metal layer 9 is made of Ti / Au; the cavity length of the single tube of the semiconductor laser is 100 μm and the width is 50 μm.

[0029] The method for fabricating the semiconductor laser with the hybrid integrated ridge waveguide structure described above includes the following steps: S1. Select substrate 1, and use metal-organic chemical vapor deposition process to sequentially grow N confinement layer 2, N waveguide layer 3, quantum well active layer 4, P waveguide layer 5, P confinement layer 6 and ohmic contact layer 8 on substrate 1 to obtain laser epitaxial wafer. S2. Spin-coat photoresist onto the surface of the ohmic contact layer 8, perform ultraviolet lithography, development, etching and photoresist removal steps, etch away the ohmic contact layer 8 except for the ridge waveguide 7 according to the preset pattern, spin-coat photoresist again, perform ultraviolet lithography, development, etching and photoresist removal steps, etch out the ridge waveguide 7, groove 10 and shoulder 11 structure according to the preset structural pattern to form the ridge waveguide 7; S3. Spin-coat photoresist on the surface of the ridge waveguide 7, and perform ultraviolet lithography, development, etching and photoresist removal steps to etch a deep trench structure that is thin in the middle and thick on both sides according to the preset structural pattern. S4. Deposit nonlinear saturated absorber material 13 in the deep trench structure by magnetron sputtering; S5. An insulating layer 12 is grown using PECVD technology in the structure. Then, photoresist is spin-coated on the surface of the insulating layer 12, and ultraviolet lithography, development, etching and photoresist removal steps are performed to etch away the insulating layer 12 except for the ridge waveguide 7, leaving a window to expose the ohmic contact layer 8. S6. Spin-coat photoresist onto the structure, perform ultraviolet lithography and development, retain the photoresist at the boundary according to the preset structural pattern, deposit the P-side metal layer 9 on the surface using electron beam evaporation deposition technology, and then use a stripping technique to remove the photoresist and metal at the boundary. S7. Thinning and polishing the side of substrate 1 away from the P-side metal to reduce the thickness of substrate 1 to 100μm, and depositing N-side metal on the thinned and polished side. S8. The wafer is cleaved, coated, and packaged to produce a semiconductor laser.

[0030] Example 2 A semiconductor laser with a hybrid integrated ridge waveguide structure, such as Figures 1-2As shown, from bottom to top, the structure includes a substrate 1, an N-confinement layer 2, an N-waveguide layer 3, a quantum well active layer 4, a P-waveguide layer 5, and a P-confinement layer 6. The upper surface of the P-confinement layer 6 has two parallel grooves 10. The region between the two grooves 10 forms a ridge waveguide 7 extending along the cavity length direction. The outer regions of the two grooves 10 form shoulders 11. A deep trench structure is provided at the output end of the ridge waveguide 7. The width of the deep trench structure and the width of the ridge waveguide 7 are both 10 μm. The height of the ridge waveguide 7 is 1 μm, and the depth of the deep trench structure is 3 μm. The deep trench structure is H-shaped along the cavity length direction of the ridge waveguide. The two side regions within 3μm of each other of the deep trench structure have a length of 25μm along the cavity length direction. The middle region between the two side regions has a length of 10μm. The middle region and the two side regions are interconnected and together form an "H"-shaped deep trench structure. The deep trench structure is filled with a nonlinear saturated absorber material 13. The upper surface of the ridge waveguide 7 is covered with an ohmic contact layer 8. An insulating layer 12 is covered on the P-confining layer 6 outside the ridge waveguide 7 region. The ohmic contact layer 8 and the insulating layer 12 are covered with a P-plane metal layer 9. The back side of the substrate 1 is covered with an N-plane metal layer.

[0031] The nonlinear saturated absorber 13 has a Spinel substrate, is doped with Co, and has a doping concentration of 0.5 at.%. The substrate 1 is an InP wafer with a crystal orientation of (100) and a thickness of 500 μm; the N-confinement layer 2 is made of AlInP and has a thickness of 2 μm; the N-waveguide layer 3 is made of AlInP and has a thickness of 2 μm; the quantum well active layer 4 is composed of GaInP, AlGaInP, and GaInP layers stacked from bottom to top, with a thickness of 40 nm; the P-confinement layer 6 is made of AlInP and has a thickness of 1 μm; the P-waveguide layer 5 is made of AlInP and has a thickness of 1 μm; the insulating layer 12 is made of SiO2 and has a thickness of 50 nm; the P-plane metal layer 9 is made of Ti / Au; the cavity length of the single tube of the semiconductor laser is 500 μm and the width is 100 μm.

[0032] The method for fabricating the semiconductor laser with the hybrid integrated ridge waveguide structure described above includes the following steps: S1. Select substrate 1, and use metal-organic chemical vapor deposition process to sequentially grow N confinement layer 2, N waveguide layer 3, quantum well active layer 4, P waveguide layer 5, P confinement layer 6 and ohmic contact layer 8 on substrate 1 to obtain laser epitaxial wafer. S2. Spin-coat photoresist onto the surface of the ohmic contact layer 8, perform ultraviolet lithography, development, etching and photoresist removal steps, etch away the ohmic contact layer 8 except for the ridge waveguide 7 according to the preset pattern, spin-coat photoresist again, perform ultraviolet lithography, development, etching and photoresist removal steps, etch out the ridge waveguide 7, groove 10 and shoulder 11 structure according to the preset structural pattern to form the ridge waveguide 7; S3. Spin-coat photoresist onto the surface of the ridge waveguide 7, and perform ultraviolet lithography, development, etching, and photoresist removal steps to etch a deep trench structure according to the preset structural pattern. S4. Deposit nonlinear saturated absorber material 13 in the deep trench structure by magnetron sputtering; S5. An insulating layer 12 is grown using PECVD technology in the structure. Then, photoresist is spin-coated on the surface of the insulating layer 12, and ultraviolet lithography, development, etching and photoresist removal steps are performed to etch away the insulating layer 12 except for the ridge waveguide 7, leaving a window to expose the ohmic contact layer 8. S6. Spin-coat photoresist onto the structure, perform ultraviolet lithography and development, retain the photoresist at the boundary according to the preset structural pattern, deposit the P-side metal layer 9 on the surface using electron beam evaporation deposition technology, and then use a stripping technique to remove the photoresist and metal at the boundary. S7. Thinning and polishing the side of substrate 1 away from the P-side metal to reduce the thickness of substrate 1 to 100μm, and depositing N-side metal on the thinned and polished side. S8. The wafer is cleaved, coated, and packaged to produce a semiconductor laser.

[0033] Example 3 A semiconductor laser with a hybrid integrated ridge waveguide structure, such as Figures 1-2As shown, from bottom to top, the structure includes a substrate 1, an N-confinement layer 2, an N-waveguide layer 3, a quantum well active layer 4, a P-waveguide layer 5, and a P-confinement layer 6. The upper surface of the P-confinement layer 6 has two parallel grooves 10. The region between the two grooves 10 forms a ridge waveguide 7 extending along the cavity length direction. The outer regions of the two grooves 10 form shoulders 11. A deep groove structure is provided at the output end of the ridge waveguide 7. The width of the deep groove structure and the width of the ridge waveguide 7 are both 15 μm. The height of the ridge waveguide 7 is 0.1 μm, and the depth of the deep groove structure is 0.2 μm. The deep groove structure is H-shaped along the cavity length direction of the ridge waveguide. The deep trench structure has a shaped distribution, with two side regions within 5 μm of each side edge, each 50 μm long along the cavity length direction. The middle region between the two side regions has a length of 30 μm. The middle region is interconnected with the two side regions, forming an "H"-shaped deep trench structure. The deep trench structure is filled with a nonlinear saturated absorber material 13. The upper surface of the ridge waveguide 7 is covered with an ohmic contact layer 8. An insulating layer 12 is covered on the P-confining layer 6 outside the ridge waveguide 7 region. A P-plane metal layer 9 is covered on top of the ohmic contact layer 8 and the insulating layer 12. An N-plane metal layer is covered on the back side of the substrate 1.

[0034] The nonlinear saturated absorber 13 has a substrate of yttrium aluminum garnet, is doped with V, and has a doping concentration of 0.5 at.%. The substrate 1 is a GaAs wafer with a crystal orientation of (100) and a thickness of 500 μm; the N-confinement layer 2 is made of AlGaAs and has a thickness of 3 μm; the N-waveguide layer 3 is made of AlGaAs and has a thickness of 3 μm; the quantum well active layer 4 is composed of GaInP, AlGaInP, and GaInP layers stacked from bottom to top, with a thickness of 40 nm; the P-confinement layer 6 is made of AlGaAs and has a thickness of 0.05 μm; the P-waveguide layer 5 is made of AlGaAs and has a thickness of 0.05 μm; the insulating layer 12 is made of SiO2 and has a thickness of 500 nm; the P-plane metal layer 9 is made of Ti / Au; the cavity length of the single tube of the semiconductor laser is 1000 μm and the width is 500 μm.

[0035] The method for fabricating the semiconductor laser with the hybrid integrated ridge waveguide structure described above includes the following steps: S1. Select substrate 1, and use metal-organic chemical vapor deposition process to sequentially grow N confinement layer 2, N waveguide layer 3, quantum well active layer 4, P waveguide layer 5, P confinement layer 6 and ohmic contact layer 8 on substrate 1 to obtain laser epitaxial wafer. S2. Spin-coat photoresist onto the surface of the ohmic contact layer 8, perform ultraviolet lithography, development, etching and photoresist removal steps, etch away the ohmic contact layer 8 except for the ridge waveguide 7 according to the preset pattern, spin-coat photoresist again, perform ultraviolet lithography, development, etching and photoresist removal steps, etch out the ridge waveguide 7, groove 10 and shoulder 11 structure according to the preset structural pattern to form the ridge waveguide 7; S3. Spin-coat photoresist onto the surface of the ridge waveguide 7, and perform ultraviolet lithography, development, etching, and photoresist removal steps to etch a deep trench structure according to the preset structural pattern. S4. Deposit nonlinear saturated absorber material 13 in the deep trench structure by magnetron sputtering; S5. An insulating layer 12 is grown using PECVD technology in the structure. Then, photoresist is spin-coated on the surface of the insulating layer 12, and ultraviolet lithography, development, etching and photoresist removal steps are performed to etch away the insulating layer 12 except for the ridge waveguide 7, leaving a window to expose the ohmic contact layer 8. S6. Spin-coat photoresist onto the structure, perform ultraviolet lithography and development, retain the photoresist at the boundary according to the preset structural pattern, deposit the P-side metal layer 9 on the surface using electron beam evaporation deposition technology, and then use a stripping technique to remove the photoresist and metal at the boundary. S7. Thinning and polishing the side of substrate 1 away from the P-side metal to reduce the thickness of substrate 1 to 100μm, and depositing N-side metal on the thinned and polished side. S8. The wafer is cleaved, coated, and packaged to prepare a semiconductor laser.

[0036] Test case The mode transmission characteristics and output beam performance of the semiconductor laser with a hybrid integrated ridge waveguide structure prepared in Example 1 were tested, and the test results are as follows: Figures 3-6 As shown. Among them, Figure 3 The far-field beam pattern of the TE0 fundamental mode propagating outside a semiconductor laser with a hybrid integrated ridge waveguide structure; by Figure 3 As can be seen, the output beam of the fundamental transverse mode exhibits a centrally symmetrical single-peak Gaussian distribution, with the light intensity concentrated at the center of the beam and gradually decreasing towards the edge. There are no obvious side lobes, distortions, or beam splitting phenomena, demonstrating good far-field beam quality. Figure 4 The far-field pattern of TE1 higher-order modes propagating outside a semiconductor laser with a hybrid integrated ridge waveguide structure; by Figure 4 It is evident that after passing through the nonlinear saturated absorption material within the ridge waveguide, the output intensity of the higher-order transverse mode is significantly attenuated, and its far-field peak intensity is significantly lower than that of the fundamental transverse mode, thus effectively suppressing the output proportion of the higher-order transverse mode. Figure 5The figure shows the propagation of the TE0 fundamental mode within the hybrid integrated ridge waveguide structure of a semiconductor laser. The arrows indicate the locations of the nonlinear saturable absorber material, and the mode loss is 7.3 dB / mm. Figure 5 It can be seen that the optical field energy of the fundamental transverse mode is concentrated in the central region of the ridge waveguide. When the optical field passes through the nonlinear saturated absorption material section, the high optical power density in the central region triggers the saturated absorption effect of the material, and the absorption capacity of the material decreases significantly. The optical field does not show obvious intensity attenuation and still maintains a complete single-peak optical field shape after passing through the absorption region, indicating that the transmission loss of the fundamental transverse mode is extremely low under this structure. Figure 6 The figure shows the propagation of the TE1 higher-order mode within the hybrid integrated ridge waveguide structure of a semiconductor laser. The arrows indicate the locations of the nonlinear saturable absorber material, and the mode loss is 27.9 dB / mm. Figure 6 It can be seen that the optical field energy of the higher-order transverse mode is mainly distributed in the two sides of the ridge waveguide, which corresponds exactly to the thick regions on both sides of the nonlinear saturable absorbing material. The optical power density in this region does not reach the saturation absorption threshold of the material, and the material maintains a strong absorption state. The intensity of the optical field is significantly attenuated after passing through the absorption region, indicating that the higher-order transverse mode is introduced with extremely high selective loss in this structure.

[0037] Figure 7 This is a transmittance characteristic curve of a nonlinear saturable absorber. As can be seen from the graph, this material exhibits typical nonlinear saturable absorption behavior: at low light power densities, the material has strong absorption and low transmittance (initial transmittance approximately 27%); as the incident light power density increases, the transmittance rises rapidly; when the power density exceeds the saturation threshold (approximately 20 W / cm²), the transmittance increases further. 2 After absorption reaches saturation, transmittance enters a stable plateau region (saturation transmittance of approximately 74%). This nonlinear absorption characteristic is the physical basis for achieving higher-order mode filtering: the optical energy of the fundamental transverse mode is concentrated in the center of the ridge waveguide, corresponding to a region where the nonlinear saturable absorbing material is thinner, resulting in high optical power density and easy attainment of the saturation threshold. After triggering saturable absorption, transmittance is high and transmission loss is low. The optical energy of the higher-order transverse modes is distributed on both sides of the ridge waveguide, corresponding to a region where the nonlinear saturable absorbing material is thicker, resulting in low optical power density and inability to trigger saturable absorption. The material remains in a strong absorption state, and higher-order modes are significantly lost, thereby achieving mode screening and improving the purity of the fundamental mode.

[0038] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A semiconductor laser with a hybrid integrated ridge waveguide structure, characterized in that, The structure comprises, from bottom to top, a substrate and a stacked structure. The upper surface of the stacked structure has two parallel grooves. The area between the two grooves forms a ridge waveguide extending along the cavity length direction. The outer areas of the two grooves form shoulders. The output end of the ridge waveguide has a deep groove structure. The deep groove structure is distributed in an "H" shape along the cavity length direction of the ridge waveguide. The deep groove structure is filled with a nonlinear saturable absorption material.

2. The semiconductor laser with a hybrid integrated ridge waveguide structure as described in claim 1, characterized in that, The width of the deep trench structure and the width of the ridge waveguide are both 1.2~15μm.

3. The semiconductor laser with a hybrid integrated ridge waveguide structure as described in claim 1, characterized in that, The length of the ridge waveguide is the same as the cavity length of a single semiconductor laser tube, and the height of the ridge waveguide is 0.1~5μm.

4. The semiconductor laser with a hybrid integrated ridge waveguide structure as described in claim 1, characterized in that, The depth of the deep groove structure is 0.2~3μm.

5. The semiconductor laser with a hybrid integrated ridge waveguide structure as described in claim 1, characterized in that, Along the cavity length direction of the ridge waveguide, the length of the two sides of the deep groove structure is 2~50μm, and the length of the middle part of the deep groove structure is 0.2~45μm; and the length of the two sides of the deep groove structure is greater than the length of the middle part of the deep groove structure.

6. The semiconductor laser with a hybrid integrated ridge waveguide structure as described in claim 1, characterized in that, The substrate of the nonlinear saturated absorber is yttrium aluminum garnet or spinel, and the doping elements are Cr, V or Co.

7. The semiconductor laser with a hybrid integrated ridge waveguide structure as described in claim 6, characterized in that, The doping concentration of the dopant element is 0.1 at.% to 5 at.%.

8. The semiconductor laser with a hybrid integrated ridge waveguide structure as described in claim 1, characterized in that, The stacked structure, from bottom to top, includes an N-confinement layer, an N-waveguide layer, a quantum well active layer, a P-waveguide layer, and a P-confinement layer. The bottom of the deep trench structure is in direct contact with the upper surface of the quantum well active layer.

9. The semiconductor laser with a hybrid integrated ridge waveguide structure as described in claim 1, characterized in that, The upper surface of the ridge waveguide is covered with an ohmic contact layer, and the stacked structure outside the ridge waveguide region is covered with an insulating layer. The ohmic contact layer and the insulating layer are covered with a P-plane metal layer. The insulating layer is made of any one of SiO2, Si3N4 or AlN. The P-plane metal layer is made of at least two of titanium, platinum, gold, nickel, germanium, chromium and tin.

10. A method for fabricating a semiconductor laser with a hybrid integrated ridge waveguide structure as described in claims 1-9, characterized in that, Includes the following steps: S1. Select a substrate and use metal-organic chemical vapor deposition to grow a stacked structure and an ohmic contact layer on the substrate in sequence to obtain a laser epitaxial wafer. S2. Ridge waveguides are formed on the epitaxial wafer of a laser using photolithography and etching techniques; S3. Photolithographic etching is performed in the output region of the ridge waveguide to form a deep trench structure; S4. Deposit a layer of nonlinear saturated absorber material within the deep trench structure; S5. Subsequently, an insulating layer is deposited on the surface of the region outside the ridge waveguide of the laser epitaxial wafer; S6. Subsequently, a P-plane metal layer is deposited on the surface of the laser epitaxial wafer, and an N-plane metal layer is deposited on the back side of the substrate. After cleaving and coating, a semiconductor laser is obtained.

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