Highly coupled modulation single-mode laser and preparation method thereof

Abstract

The invention relates to the technical field of lasers, in particular to a highly-coupled modulation single-mode laser and a preparation method thereof.The highly-coupled modulation single-mode laser comprises a coupling module and two light-emitting modules, the light-emitting surfaces of the two light-emitting modules are located on the same side, the coupling module is located on one side of the light-emitting surfaces of the light-emitting modules, and two parallel light channels are arranged in the coupling module; the ends of the two light channels are right opposite to the light-emitting faces of the two light-emitting modules respectively, a light outlet is formed in the side, away from the light-emitting modules, of the coupling module, the ends, away from the light-emitting modules, of the two light channels are converged and communicated with the light outlet, and a wave locking ring is arranged between the two light channels. Laser emitted by the two light emitting modules enters the two light channels respectively, is coupled when passing through the wave locking ring, and is finally discharged from the light outlet. According to the invention, the two light-emitting modules and the wave-locked ring are integrated on one chip, so that the design cost can be reduced and the size of the module can be reduced in subsequent packaging, no redundant spatial light path exists, and the reliability and the service life of the module are greatly improved.

Description

Technical Field

[0001] This application relates to the technical field of lasers, and in particular to a highly coupled modulated single-mode laser and its fabrication method. Background Technology

[0002] High-power single-mode 980 nm semiconductor laser chips and pump modules can be widely used in optical communication, submarine communication, satellite laser and space communication, lidar and other fields. Currently, the single-mode 980 modules use spherical lenses or C-lens coupling, which have the advantages of low cost and coupling efficiency of 70%-85%; wave selection is usually achieved using VBG volume Bragg gratings, and the selected wave is coupled into an optical fiber for use.

[0003] Traditional coupling methods require multiple optical elements for collimation, coupling, and wave locking. If two or more chips are coupled, the optical path design becomes even more complex, doubling the number of spatial optical path components required. Moreover, the adhesive bonding process for fixing optical elements is prone to failure under high temperature and humidity conditions, and suffers from problems such as poor reliability due to mechanical vibration. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a highly coupled modulated single-mode laser and its fabrication method.

[0005] One objective of this application is to provide a highly coupled modulated single-mode laser, employing the following technical solution: A highly coupled modulated single-mode laser includes a coupling module and two light-emitting modules. The two light-emitting modules are arranged side by side with their light-emitting surfaces on the same side. The coupling module is located on one side of the light-emitting surface of the light-emitting modules. The coupling module has two parallel optical paths, the ends of which are respectively opposite to the light-emitting surfaces of the two light-emitting modules. The coupling module has a light-emitting port on the side away from the light-emitting modules. The ends of the two optical paths away from the light-emitting modules converge and are connected to the light-emitting port. A wave-locking ring is provided between the two optical paths.

[0006] By adopting the above technical solution, the lasers emitted by the two light-emitting modules enter two separate optical paths, are coupled when passing through the wave-locking ring, and are finally discharged from the light outlet. This application integrates two light-emitting modules and the wave-locking ring onto a single chip, which simplifies the design cost and reduces the module size in subsequent packaging. The absence of redundant optical paths significantly improves the reliability and lifespan of the module.

[0007] Preferably, the light-emitting module includes a light-emitting region and a buffer zone, the buffer zone being located between the light-emitting region and the coupling module, and the quantum wells within the buffer zone exhibiting a disordered structure.

[0008] By adopting the above technical solution, the quantum well bandgap at the buffer zone is widened, so that the laser light from the light-emitting area will not be absorbed when it passes through the buffer zone, and heat will not accumulate at the end face, thus improving the reliability and lifespan of the chip.

[0009] Preferably, the diameter R of the wave-locking ring satisfies the optical path difference formula mλ=2πnR, where m is a positive integer, λ is the wavelength of light, and n is the refractive index of light within the coupling module.

[0010] Preferably, the side of the light-emitting module away from the coupling module is provided with a high-reflectivity film.

[0011] By adopting the above technical solution, the high-reflectivity film reflects the light in the light-emitting area, ensuring that the light is emitted from the buffer zone.

[0012] Preferably, the coupling module includes a substrate and an N-sac bread layer integrated with the light-emitting module. A passive waveguide layer is provided on the N-sac bread layer, and a pattern of optical paths and wave-locking rings is formed on the passive waveguide layer.

[0013] Preferably, each of the light-emitting modules is provided with a raised ridge structure, and the two ridge structures are respectively aligned with the two light paths.

[0014] Another objective of this application is to provide a method for fabricating a highly coupled modulated single-mode laser, employing the following technical solution: A method for fabricating a highly coupled modulated single-mode laser, comprising the following steps: S1. An epitaxial layer is grown on the substrate. The epitaxial layer includes, from bottom to top, an N-faced bread layer, an N-faced waveguide layer, an active region, and a P-faced waveguide layer. S2. By photolithography and dry etching on one side, one side of the epitaxial layer is etched to the N-slab to form a coupling groove, and the other side of the epitaxial layer is the light-emitting module; S3. A SiN layer is grown on the entire surface of the epitaxial layer. The SiN in the coupling groove forms a passive waveguide layer. The height of the passive waveguide layer is not less than the height of the P-side waveguide layer in the light-emitting module. S4. Etch away the SiN above the light-emitting module and grow the P-bread layer and P-surface cap layer in sequence. S6. By photolithography and electron beam exposure, optical paths and wave-locking ring patterns are etched on the upper surface of the passive waveguide layer to form a coupling module.

[0015] By adopting the above technical solution, and introducing quantum well vacancy-induced disorder, passive waveguide selection, and coupling technologies into the chip manufacturing process, a novel and feasible process route is presented, integrating laser emission, separate coupling into passive waveguides, micro-ring wave selection, and coupled output into a single chip.

[0016] Preferably, the step of removing the SiN above the light-emitting module in S4 includes, S41. Remove the SiN above the buffer zone by dry etching; S42. A layer of SiO2 is grown on the entire epitaxial layer and then subjected to rapid thermal annealing in N2 at 930℃. S43. Dry etching is used to remove SiO2 from the entire surface. S44. Etch to remove the SiN above the light-emitting area.

[0017] By employing the above technical solution, the SiO2 layer on the buffer layer enhances the ability of Ga to diffuse outward from the semiconductor surface and generate vacancies, leading to vacancy-induced disorder in the quantum well during rapid thermal annealing and an increase in the bandgap. Meanwhile, the SiN on the light-emitting region and coupling module prevents As desorption from the surface, protecting this region from the effects of rapid thermal annealing. The key focus is on the active quantum well beneath the light-emitting region.

[0018] Preferably, the steps between S4 and S6 are also included. S51. Partially etch away the P-surface capping layer and P-sac bread layer on the upper surface of the luminescent area and buffer zone to expose the P-surface waveguide layer, forming a raised ridge structure. The ridge structure runs through the luminescent area and buffer zone and is directly opposite the optical path. S52. Two parallel ridge structures are etched on the epitaxial layer, and the two ridge structures are respectively aligned with the two optical paths; S53, SiN is grown on the entire surface of the epitaxial layer; S54. Remove the SiN above the two ridge structures by photolithography.

[0019] Preferably, the following steps are also included. S7. Seed metal Ti / Pt / Au is deposited into the luminescent area and buffer zone by metal stripping process; S8. Electroplating is performed on the seed metal to form an electroplated layer.

[0020] In summary, this application includes the following beneficial technical effects: This application integrates two light-emitting modules and a wave-locked ring onto a single chip, which simplifies design costs and reduces module size in subsequent packaging. The absence of redundant optical paths significantly improves module reliability and lifespan. The convenience and simplicity of this invention are even more pronounced when dealing with coupling between two or more chips. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1; Figure 2 This is a schematic diagram of the structure of the light-emitting module and the coupling module used in Embodiment 1; Figure 3This is a top view of the structure of Embodiment 1; Figure 4 This is a schematic diagram of the epitaxial structure in steps S1-S2 of Embodiment 2; Figure 5 This is a schematic diagram of the extensional structure in step S3 of embodiment two; Figure 6 This is a schematic diagram of the extensional structure in steps S41-S42 of Embodiment 2; Figure 7 This is a schematic diagram of the extensional structure in step S43 of Embodiment 2; Figure 8 This is a schematic diagram of the extensional structure in step S44 of Embodiment 2; Figure 9 This is a schematic diagram of the extensional structure in steps S51-S52 of Embodiment 2; Figure 10 This is a top view of the extensional structure in steps S51-S52 of Embodiment 2; Figure 11 This is a schematic diagram of the extensional structure in steps S53-S6 of Embodiment 2; Figure 12 This is a top view of the extensional structure in steps S53-S6 of Embodiment 2; Figure 13 This is a top view of the extension structure in step S9 of Embodiment 2.

[0022] Explanation of reference numerals in the attached figures: 1. Substrate; 2. N-slab bread layer; 3. N-plane waveguide layer; 4. Active region; 5. P-plane waveguide layer; 6. P-plane capping layer; 7. P-slab bread layer; 8. Ridge structure; 9. Light-emitting module; 10. Coupling module; 11. Light-emitting area; 12. Buffer zone; 13. Optical path; 14. Circular path; 15. Wave-locking ring; 16. Light-emitting port; 17. High-reflection film; 18. Passive waveguide layer; 19. Seed gold; 20. Electroplating layer; 21. N-gold. Detailed Implementation

[0023] The present application will be further described in detail below with reference to all the accompanying drawings.

[0024] Example 1

[0025] This application discloses a highly coupled modulated single-mode laser, with reference to... Figures 1 to 3 It includes a substrate 1, on which an epitaxial layer is grown. The epitaxial layer includes an N-faced bread layer 2, an N-faced waveguide layer 3, an active region 4, and a P-faced waveguide layer 5 arranged sequentially from bottom to top.

[0026] Reference Figures 1 to 3The epitaxial layer is divided into two regions: a light-emitting region and a coupling region. Two light-emitting modules 9 are formed within the light-emitting region, and a coupling module 10 is formed within the coupling region. The lasers emitted by the two light-emitting modules 9 are coupled through the coupling module 10, ultimately forming a single laser beam. This achieves the integration of two laser modules and one coupling module 10, thereby reducing the module size. Furthermore, the solution in this application has no redundant spatial optical paths, significantly improving the reliability and lifespan of the module.

[0027] Reference Figures 1 to 3 Two light-emitting modules 9 are arranged side by side, with their light-emitting surfaces on the same side. A high-reflectivity film 17 is provided on the back surface of both light-emitting modules 9 to ensure that the laser light is emitted from the light-emitting surface. A coupling module 10 is located on one side of the light-emitting surface of the light-emitting module 9.

[0028] Reference Figures 1 to 3 The light-emitting module 9 includes a light-emitting region 11 and a buffer zone 12. The buffer zone 12 is located between the light-emitting region 11 and the coupling module 10, and the quantum well within the buffer zone 12 has a disordered structure. The energy band of the quantum well at the buffer zone 12 is widened, so that the laser light from the light-emitting region 11 is not absorbed when passing through the buffer zone 12, preventing heat accumulation at the end face and improving the reliability and lifespan of the chip. Each light-emitting module 9 has a raised ridge structure 8 that runs through the light-emitting region 11 and the buffer zone 12.

[0029] Reference Figures 1 to 3 The substrate 1 and N-slab 2 in the coupling module 10 are integrally formed with the substrate 1 and N-slab 2 in the light-emitting module 9. A passive waveguide layer 18 is provided on the N-slab 2 of the coupling module 10. The passive waveguide layer 18 is made of SiN and has a pattern of light path 13 and wave lock ring 15 formed by etching.

[0030] Reference Figures 1 to 3 Two parallel optical channels 13 are provided, with the ends of the two optical channels 13 facing the two ridge structures 8 respectively. The coupling module 10 has an arc-shaped channel 14 connecting the two optical channels 13 on the side opposite to the light-emitting module 9. The two laser beams emitted by the two light-emitting modules 9 enter the two optical channels 13 and converge through the arc-shaped channel 14.

[0031] Reference Figures 1 to 3 The coupling module 10 has a light outlet 16 on the side away from the light-emitting module 9. The light outlet 16 is located in the middle of the arc path 14, and the arc path 14 is connected to the light outlet 16. The converging laser beams are finally emitted from the light outlet 16.

[0032] Reference Figures 1 to 3The wavelock ring 15 is circular and located between the two optical paths 13. The diameter R of the wavelock ring 15 satisfies the optical path difference formula mλ=2πnR, where m is a positive integer, λ is the wavelength of light, and n is the refractive index of the passive waveguide layer 18 in the coupling module 10. For example, to output a single-mode laser with a wavelength of 974nm, n is 2, and m is 20, then the radius R of the wavelock ring 15 is 3.1um.

[0033] Example 2

[0034] This application discloses a method for fabricating a highly coupled modulated single-mode laser, used to fabricate a highly coupled modulated single-mode laser as described in the above embodiments. The method includes the following steps, with this embodiment using a 980nm wavelength as an example. Reference Figure 4 S1. First, grow the epitaxial structure, which from bottom to top is substrate 1, N-slab 2, N-plane waveguide layer 3, active region 4 and P-plane waveguide layer 5.

[0035] Reference Figure 4 S2. Through a single photolithography and dry etching process, the epitaxial structure of the coupling region is etched down to part of the N-cladding layer to form a coupling groove. The other side of the epitaxial layer is the light-emitting region.

[0036] Reference Figure 5 S3. Remove the photoresist and clean the surface. Grow a SiN layer using PECVD. The height of the SiN growth at the coupling groove is the same as or slightly higher than the P-side waveguide layer 5 in the light-emitting area. The SiN in the coupling groove forms a passive waveguide layer 18.

[0037] Reference Figure 6 S41. Remove the SiN in buffer 12 by dry etching through a single photolithography process; remove the resist and clean.

[0038] Reference Figure 6 In step S42, a SiO2 layer is grown using PECVD and then subjected to rapid thermal annealing in N2 at 930°C. The SiO2 layer on buffer zone 12 enhances Ga diffusion from the semiconductor surface and generates vacancies, leading to quantum well vacancy-induced disorder and a wider bandgap during rapid thermal annealing. Meanwhile, the SiN layer under the light-emitting region 11 and the coupling region prevents As desorption from the surface, protecting this region from the effects of rapid thermal annealing. The key focus is protecting the active region 4 quantum well beneath the light-emitting region 11; the quantum well beneath the coupling region has already been etched away.

[0039] Reference Figure 7 S43. The entire surface is etched using dry self-aligned etching, without photolithography, to remove SiO2 from the surface. The light-emitting area 11 and the coupling area are stopped at the SiN below or partially etched. The buffer zone 12 is stopped above the P waveguide, and the P waveguide layer is etched as little as possible.

[0040] Reference Figure 8 S44. The SiN above the light-emitting region 11 is removed using photolithography and wet etching. The photoresist above the light-emitting region 11 is removed and cleaned. Then, a secondary epitaxial growth of the P-bread layer 7 and the P-surface capping layer 6 continues. At this point, the traditional 980 epitaxial structure's light-emitting region, the quantum well vacancy-induced disorder buffer zone 12, and the coupling region of the unwired waveguide have been grown. Chip fabrication then commences.

[0041] First, the ridge portion is fabricated. This structure is crucial for generating a single mode in the light-emitting region, primarily providing longitudinal current injection constraint as well as transverse refractive index and optical field mode constraint.

[0042] Reference Figure 9 and Figure 10 S51. Through photolithography and etching, the P-side capping layer 6, P-side breading layer 7, and part of the P-side waveguide layer 5 are etched away above the light-emitting region 11 and the buffer zone 12, forming a raised ridge structure 8. The ridge structure 8 penetrates the light-emitting region 11 and the buffer zone 12; due to the presence of SiN, the coupling region will stop on the SiN after the P-side capping layer 6 and P-side breading layer 7 are etched away, because the etching rate of the etching gas to SiN is very slow, and the loss is acceptable. In terms of size: the ridge structure 8 is 4 μm wide and 2400 μm long.

[0043] Reference Figure 9 and Figure 10 S52, repeat S51, etching to form two parallel ridge structures 8.

[0044] Reference Figure 11 and Figure 12 After etching the S53 ridge, a 130nm thick insulating SiN layer is grown across the entire surface. Then, photoresist is spin-coated, with the photoresist height controlled to be slightly higher than the surface SiN.

[0045] Reference Figure 11 and Figure 12 S54. Using self-aligned etching, after partially etching the photoresist using dry etching, remove the SiN on the ridge structure 8, thereby opening the ridge structure 8, and then etch the photoresist in other areas. After etching, remove the residual photoresist and clean thoroughly.

[0046] Reference Figure 11 and Figure 12S6. Through photolithography and electron beam exposure, the light-emitting area 11 and the buffer zone 12 are covered. The coupling region is etched with SiN passive waveguides to form the optical path 13 and wave-locking ring 15 patterns, forming the coupling module 10. The etching depth is 300nm; the total length of the coupling module 10 is 100um, the width of the optical path 13 is 5um, the radius of the central wave-locking ring 15 is 3um, the width is 500nm, and the distance from the edge of the wave-locking ring 15 to the optical path 13 is 150nm; the radius of the arc path 14 is 3.65um. Finally, the resist is removed and the area is cleaned.

[0047] Reference Figure 13 S7. Seed gold Ti / Pt / Au is deposited in the light-emitting area 11 and buffer zone 12 by metal stripping process, and the seed gold and photoresist of coupling module 10 are stripped off.

[0048] Reference Figure 13 S8. Electroplating is performed on the seed gold to form an electroplating layer with a thickness of about 3 μm. At this point, the P-side process is complete.

[0049] Reference Figure 13 After thinning and polishing the S9 and N surfaces, N gold is grown, followed by rapid thermal annealing. Finally, a high-reflectivity film of 17% to 96% is deposited on the left end face of the luminescent area 11.

[0050] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A highly coupled modulated single-mode laser, characterized in that: The device includes a coupling module (10) and two light-emitting modules (9). The two light-emitting modules (9) are arranged side by side, and the light-emitting surfaces of the two light-emitting modules (9) are located on the same side. The coupling module (10) is located on one side of the light-emitting surface of the light-emitting module (9). The coupling module (10) has two parallel light channels (13). The ends of the two light channels (13) are respectively facing the light-emitting surfaces of the two light-emitting modules (9). The side of the coupling module (10) away from the light-emitting module (9) has a light outlet (16). The ends of the two light channels (13) away from the light-emitting module (9) converge and are connected to the light outlet (16). A wave-locking ring (15) is provided between the two light channels (13).

2. The highly coupled modulated single-mode laser according to claim 1, characterized in that: The light-emitting module (9) includes a light-emitting region (11) and a buffer (12). The buffer (12) is located between the light-emitting region (11) and the coupling module (10). The quantum well in the buffer (12) has a disordered structure.

3. A highly coupled modulated single-mode laser according to claim 1, characterized in that: The diameter R of the wave-locking ring (15) satisfies the optical path difference formula mλ=2πnR, where m is a positive integer, λ is the wavelength of light, and n is the refractive index of light in the coupling module (10).

4. A highly coupled modulated single-mode laser according to claim 1, characterized in that: The light-emitting module (9) has a high-reflectivity film (17) on the side away from the coupling module (10).

5. A highly coupled modulated single-mode laser according to claim 1, characterized in that: The coupling module (10) includes a substrate (1) and an N-bread layer (2) integrated with the light-emitting module (9). A passive waveguide layer (18) is provided on the N-bread layer (2), and a pattern of light path (13) and wave lock ring (15) is formed on the passive waveguide layer (18).

6. A highly coupled modulated single-mode laser according to claim 1, characterized in that: Each of the light-emitting modules (9) is provided with a raised ridge structure (8), and the two ridge structures (8) are respectively opposite to the two light channels (13).

7. A method for fabricating a highly coupled modulated single-mode laser, characterized in that: The method for fabricating a highly coupled modulated single-mode laser as described in any one of claims 1-6 includes the following steps. S1. An epitaxial layer is grown on a substrate (1). The epitaxial layer includes an N-faced bread layer (2), an N-faced waveguide layer (3), an active region (4), and a P-faced waveguide layer (5) arranged sequentially from bottom to top. S2. By photolithography and dry etching on one side, one side of the epitaxial layer is etched to the N-slab (2) to form a coupling groove, and the other side of the epitaxial layer is the light-emitting module (9); S3. A layer of SiN is grown on the entire surface of the epitaxial layer, and the SiN in the coupling groove forms a passive waveguide layer (18). The height of the passive waveguide layer (18) is not lower than the height of the P-side waveguide layer (5) inside the light-emitting module (9). S4. Etch away the SiN above the light-emitting module (9) and grow the P-bread layer (7) and the P-surface cap layer (6) in sequence. S6. By photolithography and electron beam exposure, the optical path (13) and wave-locking ring (15) pattern are etched on the upper surface of the passive waveguide layer (18) to form a coupling module (10).

8. The method for fabricating a highly coupled modulated single-mode laser according to claim 7, characterized in that: The steps in S4 to remove the SiN above the light-emitting module (9) include: S41. Remove the SiN above the buffer zone (12) by dry etching; S42. A layer of SiO2 is grown on the entire epitaxial layer and then subjected to rapid thermal annealing in N2 at 930℃. S43. Dry etching is used to remove SiO2 from the entire surface. S44, Etch away the SiN above the light-emitting area (11).

9. The method for fabricating a highly coupled modulated single-mode laser according to claim 7, characterized in that: It also includes steps located between S4 and S6. S51. Partial etching is performed on the upper surface of the light-emitting area (11) and the buffer zone (12) to remove the P-surface capping layer (6) and the P-bread layer (7), exposing the P-surface waveguide layer (5) and forming a raised ridge structure (8). The ridge structure (8) penetrates the light-emitting area (11) and the buffer zone (12) and is directly opposite the optical path (13). S52. Two parallel ridge structures (8) are etched on the epitaxial layer, and the two ridge structures (8) are directly opposite to the two optical paths (13); S53, SiN is grown on the entire surface of the epitaxial layer; S54. Remove the SiN above the two ridge structures (8) by photolithography.

10. The method for fabricating a highly coupled modulated single-mode laser according to claim 9, characterized in that: It also includes the following steps, S7. Seed metal Ti / Pt / Au is deposited on the light-emitting area (11) and the buffer zone (12) by metal stripping process; S8. Electroplating is performed on the seed metal to form an electroplated layer.

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