Multi-cell multi-grating multi-wavelength ultra-narrow linewidth vertical surface emitting laser array

Abstract

The application relates to the technical field of semiconductor lasers, in particular to a multi-unit multi-grating multi-wavelength ultra-narrow linewidth vertical surface emitting laser array which is composed of N rows and M columns of ridge-back semiconductor lasers; N and M are positive integers, each ridge-back semiconductor laser corresponds to a unique coordinate (N, M) and a matched grating constant Lambda (N,M) and an output wavelength Lambda (N,M) . The ridge-back semiconductor laser comprises a substrate, a back-ridge optical waveguide arranged at the upper end surface of the substrate, a vertical HR end surface and an inclined angle HR end surface; the back-ridge optical waveguide comprises a light-emitting quantum well layer, a multilayer deep-buried semiconductor DFB grating, a PN junction and an upper end surface composite functional grating which are integrated in the back-ridge optical waveguide. In the application, the multi-grating synergic structure of the upper end surface composite functional grating and the multilayer deep-buried semiconductor DFB grating has a comprehensive light filtering efficiency which is far superior to that of a traditional single-layer grating, and the ultra-narrow linewidth (0.1-2 kHz) output is realized.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, specifically to a multi-unit, multi-grating, multi-wavelength, ultra-narrow linewidth vertical-plane emitting laser array. Background Technology

[0002] Current vertical-cavity surface-emitting lasers (VCSELs) and distributed feedback lasers (DFBs) still have several key technological shortcomings in high-performance optoelectronic applications, as follows:

[0003] Technical limitations of traditional VCSELs

[0004] The output linewidth is too wide, typically around 5MHz, which makes it difficult to meet the spectral purity requirements of scenarios such as high-precision spectral measurement, narrowband optical communication, and AI optical computing chips.

[0005] Commercial devices operate in the 800–1000 nm near-infrared band. VCSELs in the 1550 nm band are limited by the inherent small refractive index difference of the material system, and their overall performance and cost control level are still far from large-scale commercial applications.

[0006] The output power of single-tube devices is relatively low, with a typical value of only about 0.2mW. The power density is insufficient, making it difficult to meet the needs of high-end application scenarios such as AI optical computing chips, long-distance optical communication and sensing.

[0007] Array devices generally suffer from the problem of single-unit wavelength, which makes it impossible to achieve dense wavelength division multiplexing (DWDM) wavelength sequence output that conforms to the ITU-T Grid standard, thus limiting their application in high-capacity optical interconnect systems.

[0008] Technical limitations of traditional DFB lasers

[0009] The use of edge emitter (EEL) structures is limited by the chip's light emission direction and fabrication process, making it difficult to achieve large-area, high-density, and low-cost integration of two-dimensional vertical-plane emitting laser arrays.

[0010] Conventional 1550nm DFB lasers typically have an output linewidth of 100kHz or higher, which cannot meet the stringent performance requirements for spectral narrowing in ultra-narrow linewidth (0.1–5kHz) AI optical matrix computing chips, quantum communication optical chips, and other applications.

[0011] Traditional DFB laser wafer-level wavelength modulation schemes are mostly single-wavelength designs, relying on cumbersome wafer-level process optimization, making it difficult to achieve precise multi-wavelength matching of each unit in the array, and failing to efficiently meet the high-density integration application requirements that comply with ITU-T Grid wavelength standards.

[0012] To address these issues, the industry has attempted to optimize the grating structure and resonant cavity design, but none of these efforts have broken through the architectural limitations of traditional DFB lasers. They have failed to achieve integrated functionality of filtering, electrodes, and coupled output, nor have they been able to avoid the high complexity of traditional grating processes. The problem of switching from edge emission to vertical plane emission remains unsolved, which restricts the performance improvement and cost control of multi-wavelength laser source arrays. Summary of the Invention

[0013] This invention addresses the core pain points of existing DFB edge-emitting lasers, such as insufficient linewidth, complex manufacturing processes, high costs, poor performance consistency, limited output direction, and low integration. It provides a multi-unit spine-type multi-wavelength vertical-emitting laser source array. Through an integrated composite functional grating design and an internal cavity quasi-resonant cavity architecture, it avoids secondary epitaxial processes, combining the low cost and high yield advantages of FP lasers with the narrow linewidth performance of DFB lasers. This achieves vertical emission and precise multi-wavelength control, improving device stability and integration. It provides a high-performance, low-cost multi-wavelength light source solution for high-density wavelength division multiplexing and other fields, while overcoming the problems of wide linewidth, low power, and single wavelength in existing VCSELs. It provides a novel vertical-plane emitting DFB laser array with ultra-narrow linewidth horizontal cavity vertical emission based on multi-grating integrated filtering and multi-unit multi-wavelength implementation, thus solving the problems mentioned in the background art.

[0014] To achieve the above objectives, the present invention provides the following technical solution:

[0015] Based on a multi-unit, multi-grating, multi-wavelength, ultra-narrow linewidth vertical-plane emitting laser array, it consists of N rows × M columns of spine semiconductor lasers;

[0016] N and M are positive integers, and each of the spine-type semiconductor lasers corresponds to a unique coordinate (N, M) and a matching grating constant Λ. (N,M) and output wavelength λ (N,M) .

[0017] As a preferred embodiment of the above technical solution, the spine-back semiconductor laser includes:

[0018] Substrate;

[0019] A ridge-type optical waveguide is disposed on the upper end face of the substrate;

[0020] The vertical HR end face is machined on the left side of the spine-type optical waveguide;

[0021] An angled HR end face is machined on the right side of the back ridge optical waveguide, and the angle φ of the angled HR end face is 10°-26°.

[0022] The back-ridge optical waveguide includes an integrated light-emitting quantum well layer, a multilayer buried semiconductor DFB grating, a PN junction, and an upper-side composite functional grating.

[0023] The upper end face composite functional grating includes a second-order grating disposed in the middle for achieving upward output of light coupling while also taking into account some filtering effect, and a first-order filtering grating disposed on both sides of the second-order grating for achieving filtering function while also acting as laser electrode.

[0024] Each of the first-order filter gratings has a λ in its center. (N,M) A / 4 phase shift structure is used to realize that the first-order filter grating is symmetrically divided into sections with a spacing of λ. (N,M) / 4 two-segment grating.

[0025] As a preferred embodiment of the above technical solution, the upper surface of the second-order grating is coated with a layer, which is a silicon dioxide protective layer or an AR anti-reflective film.

[0026] As a preferred embodiment of the above technical solution, the multilayer buried semiconductor DFB grating includes a K-layer buried semiconductor DFB grating disposed on the upper part of the light-emitting quantum well layer and an L-layer buried semiconductor DFB grating disposed on the lower part of the light-emitting quantum well layer, where K and L are natural numbers.

[0027] As a preferred embodiment of the above technical solution, the substrate is an InP or GaAs substrate.

[0028] As a preferred embodiment of the above technical solution, both the vertical HR end face and the angled HR end face are coated with an HR optical film.

[0029] As a preferred embodiment of the above technical solution, the upper surface composite functional grating is any one of the following: a surface-reflective metal optical comb grating, a semiconductor / SiO2 etched grating with a reflective optical film deposited on the upper surface, and a vapor-deposited planar metal optical comb grating.

[0030] As a preferred embodiment of the above technical solution, the resonant structure of the spine semiconductor laser (1) is composed of a quasi-resonant cavity formed by the composite functional grating of the vertical HR end face and the upper end face; by means of the reflection wavelength selection characteristics of the first-order filter grating, the resonant cavity has narrow linewidth optical quality characteristics.

[0031] As a preferred embodiment of the above technical solution, the grating constant of the second-order grating in the same spine semiconductor laser is twice the grating constant of the first-order filter grating.

[0032] As a preferred embodiment of the above technical solution, the grating constant Λ of each unit is adjusted. (N,M) This enables each of the spine semiconductor lasers in the array to output a specific wavelength that conforms to the ITU-T standard wavelength spacing, thereby achieving the multi-wavelength integration required for high-density wavelength division multiplexing.

[0033] As a preferred embodiment of the above technical solution, the upper surface composite functional grating is an arbitrary shape grating, and its filtering function satisfies the λ of BRAGG. (N,M) / 2 grating constant; the material of the upper surface composite functional grating is metal, semiconductor, dielectric, lithium niobate, piezoelectric ceramic or plastic; the type of the upper surface composite functional grating is high reflectivity, transmission refraction or semi-transmission semi-reflection.

[0034] This invention provides a multi-unit, multi-grating, multi-wavelength, ultra-narrow linewidth vertical-plane emitting laser array, which has the following advantages:

[0035] 1. Disruptive innovation in structure and principle: The multi-grating synergistic structure of "top-side composite functional grating + multi-layer buried semiconductor DFB grating" has a comprehensive filtering efficiency far superior to that of traditional single-layer gratings, achieving ultra-narrow linewidth (0.1-2kHz) output; combined with the resonant cavity design of "vertical HR end face + oblique HR end face", it realizes the conversion from traditional DFB edge emission to vertical surface emission in the gain chip region, breaking through the limitation of optical field output direction; at the same time, it replaces the traditional single buried DFB grating, simplifying the fabrication process.

[0036] 2. High functional integration: The composite functional grating on the upper surface has three functions: filtering, electrode, and vertical coupling output. No additional corresponding structure is required, which simplifies the overall structure and fabrication process of the device and reduces the complexity of the process.

[0037] 3. Precise and efficient multi-wavelength control: By adjusting the grating constant Λ of each unit... (N,M) This allows each spine semiconductor laser in the array to output a specific wavelength that conforms to the ITU-T standard wavelength spacing, realizing the multi-wavelength integration required for high-density wavelength division multiplexing and adapting to the needs of different application scenarios.

[0038] 4. Excellent optical quality characteristics: Through the three-level synergistic effect of "preliminary filtering by multi-layer buried semiconductor DFB grating + precise screening by first-order filter grating + deep narrowing by λ / 4 phase shift structure", combined with the resonant coordination of the vertical HR end face and the multi-layer buried semiconductor DFB grating system, an ultra-narrow linewidth output of 0.1-2kHz is achieved; at the same time, the angled HR end face design eliminates lateral resonance interference, further improving the stability and quality of output light.

[0039] 5. Significant cost advantages: It simplifies the fabrication process, avoids the high complexity of traditional grating processes, improves device yield, and reduces the number of components through functional integration, thereby significantly reducing the cost of device fabrication and application, and providing a feasible path for high-performance, low-cost integrated photonic chips. Attached Figure Description

[0040] Figure 1This is a schematic diagram of an N (number of rows) × M (number of columns) array structure of a spine semiconductor laser, where N and M are positive integers; each spine semiconductor laser corresponds to a specific output wavelength λ. (N,M) and grating constant Λ (N,M) ;

[0041] Figure 2 A schematic diagram of the front cross-section of a spine-back semiconductor laser;

[0042] Figure 3 for Figure 2 Top view;

[0043] Figure 4 for Figure 2 The left view.

[0044] In the figure: 1. Ridge-back semiconductor laser; 2. Substrate; 3. Ridge-back optical waveguide; 31. Light-emitting quantum well layer; 32. PN junction; 33. Top-side composite functional grating; 331. Second-order grating; 332. First-order filter grating; 333. λ (N,M) / 4 Phase shift structure; 334 Coating; 34 Multilayer buried semiconductor DFB grating; 4 Vertical HR end face; 5 Angled HR end face. Detailed Implementation

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0046] Example

[0047] Based on a multi-unit, multi-grating, multi-wavelength, ultra-narrow linewidth vertical plane emitting laser array, it is composed of N rows × M columns of spine semiconductor lasers 1;

[0048] N and M are positive integers, and each of the spine semiconductor lasers 1 corresponds to a unique coordinate (N, M) and a matching grating constant Λ. (N,M) and output wavelength λ (N,M) .

[0049] As a preferred embodiment of the above technical solution, the spine-type semiconductor laser 1 includes:

[0050] Substrate 2;

[0051] A back-ridge type optical waveguide 3 is disposed on the upper end surface of the substrate 2;

[0052] The vertical HR end face 4 is machined on the left side of the spine-type optical waveguide 3;

[0053] The beveled HR end face 5 is machined on the right side of the back ridge optical waveguide 3, and the bevel angle φ of the beveled HR end face 5 is 10°-26°.

[0054] The back-ridge type optical waveguide 3 includes an integrated light-emitting quantum well layer 31, a multilayer buried semiconductor DFB grating 34, a PN junction 32, and an upper end face composite functional grating 33.

[0055] The upper end face composite functional grating 33 includes a second-order grating 331 disposed in the middle for realizing upward output of light coupling while also taking into account part of the light filtering effect, and a first-order filter grating 332 disposed on both sides of the second-order grating 331 for realizing the light filtering function while also serving as laser electrode.

[0056] Each of the first-order filter gratings 332 has a λ in its center. (N,M) A / 4 phase shift structure is used to realize that the first-order filter grating 332 is symmetrically divided into sections with a spacing of λ. (N,M) The grating has two segments of λ / 4; for example, for a unit with a target wavelength of 1550nm, the grating constant Λ=387.5nm; a λ / 4 phase shift structure is set in the middle of the first-order filter grating 332, with a phase shift spacing of 387.5nm, so that the grating is symmetrically divided into two segments to ensure narrow linewidth output.

[0057] The upper surface of the second-order grating 331 is coated with a coating layer 334, which is a silicon dioxide protective layer or an AR anti-reflective film.

[0058] The multilayer buried semiconductor DFB grating 34 includes a K-layer buried semiconductor DFB grating disposed on the upper part of the light-emitting quantum well layer 31 and an L-layer buried semiconductor DFB grating disposed on the lower part of the light-emitting quantum well layer 31. K and L are natural numbers (0, 1, 2, 3...) and can be flexibly adjusted according to linewidth requirements. It works in conjunction with the upper end-face composite functional grating 33 to form a comprehensive filtering system. The filtering efficiency is much greater than that of traditional single-layer gratings, significantly narrowing the laser linewidth to 0.1-2kHz, meeting the requirements of high-end application scenarios such as high resolution, strong coherence, low bit error rate, and long-distance sensing.

[0059] The substrate 2 is an InP or GaAs substrate.

[0060] Both the vertical HR end face 4 and the oblique HR end face 5 are coated with SiO2 / TiO2 multilayer HR optical films with a reflectivity >99.9%; effectively eliminating interference from the transverse end face resonant cavity and ensuring stable oscillation of the resonant light.

[0061] The upper surface composite functional grating 33 is any one of the following: a surface-reflective metal comb grating, a semiconductor / SiO2 etched grating with a reflective optical film deposited on the upper surface, and a vapor-deposited planar metal comb grating.

[0062] The resonant structure of the spine semiconductor laser 1 is a quasi-resonant cavity formed by the vertical HR end face 4 and the upper end face composite functional grating 33; by means of the reflection wavelength selection characteristics of the first-order filter grating 332, the resonant cavity has narrow linewidth optical quality characteristics.

[0063] The grating constant of the second-order grating 331 in the same spine semiconductor laser 1 is twice the grating constant of the first-order filter grating 332.

[0064] By adjusting the grating constant Λ of each unit (N,M) This enables each of the spine semiconductor lasers 1 in the array to output a specific wavelength that conforms to the ITU-T standard wavelength spacing, thereby achieving the multi-wavelength integration required for high-density wavelength division multiplexing.

[0065] The upper surface composite functional grating 33 is an arbitrary shape grating, and its filtering function satisfies the λ of BRAGG. (N,M) / 2 grating constant; the material of the upper surface composite functional grating 33 is metal, semiconductor, dielectric, lithium niobate, piezoelectric ceramic or plastic; the type of the upper surface composite functional grating 33 is high reflectivity, transmission refraction or semi-transmission semi-reflection.

[0066] The laser emission process in this embodiment is as follows: A positive bias voltage is applied to the electrodes of the first-order filter grating 332 of the upper end face composite functional grating 33, and electrons and holes are injected into the quantum well layer 31 to emit light. The generated light oscillates in the quasi-resonant cavity formed by the vertical HR end face 4 and the "upper end face composite functional grating 33 + multilayer buried semiconductor DFB grating 34". After preliminary filtering by the multilayer buried semiconductor DFB grating 34, precise screening by the first-order filter grating 332, and further narrowing of the linewidth by the λ / 4 phase shift structure, part of the light is emitted vertically upward through the opening of the middle second-order grating 331 to achieve specific wavelength output. By adjusting the grating constant of each unit, the array output can be made to conform to the ITU-Grid 100GHz spacing multi-wavelength laser, which meets the requirements of high-density wavelength division multiplexing.

[0067] Tests showed that the output wavelength of each laser unit in this embodiment accurately matches the ITU-Grid standard, the linewidth is stable in the ultra-narrow linewidth range of 0.1-2kHz, the vertical emission efficiency is >85%, and the thermal stability is excellent (wavelength drift <0.03pm / ℃ from -40℃ to 85℃). The overall filtering efficiency is more than 60% higher than that of traditional single-layer gratings, and the fabrication process is more than 40% simpler than that of traditional DFB multi-wavelength arrays, with a cost reduction of more than 50%.

[0068] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A vertically emitting laser array based on multi-unit, multi-grating, multi-wavelength, ultra-narrow linewidth laser, characterized in that: It consists of N rows × M columns of spine-back semiconductor lasers (1); N and M are positive integers, and each of the spine semiconductor lasers (1) corresponds to a unique coordinate (N, M) and a matching grating constant Λ. (N,M) and output wavelength λ (N,M) ; The spine-type semiconductor laser (1) includes: Substrate (2); A back-ridge type optical waveguide (3) is disposed on the upper end surface of the substrate (2); The vertical HR end face (4) is machined on the left side of the back ridge optical waveguide (3); The angled HR end face (5) is machined on the right side of the back ridge optical waveguide (3), and the angle φ of the angled HR end face (5) is 10°-26°. The back-ridge type optical waveguide (3) includes a light-emitting quantum well layer (31), a multilayer buried semiconductor DFB grating (34), a PN junction (32), and an upper end face composite functional grating (33) integrated therein. The upper surface composite functional grating (33) includes a second-order grating (331) disposed in the middle for realizing upward output of light coupling while also taking into account some filtering effect, and a first-order filtering grating (332) disposed on both sides of the second-order grating (331) for realizing filtering function while also serving as laser electrode. The first-order filter grating (332) is provided with λ in the middle. (N,M) A / 4 phase shift structure is used to realize that the first-order filter grating (332) is symmetrically divided into sections with a spacing of λ. (N,M) / 4 two-segment grating; The multilayer buried semiconductor DFB grating (34) includes a K-layer buried semiconductor DFB grating disposed on the upper part of the light-emitting quantum well layer (31) and an L-layer buried semiconductor DFB grating disposed on the lower part of the light-emitting quantum well layer (31), where K and L are natural numbers.

2. The multi-unit spine-type multi-wavelength vertical emission laser source array according to claim 1, characterized in that: The upper surface of the second-order grating (331) is coated with a coating (334), which is a silicon dioxide protective layer or an AR anti-reflective film.

3. The vertical-plane emitting laser array based on multi-unit, multi-grating, multi-wavelength, ultra-narrow linewidth as described in claim 1, characterized in that: The substrate (2) is an InP or GaAs substrate.

4. The vertical-plane emitting laser array based on multi-unit, multi-grating, multi-wavelength, ultra-narrow linewidth as described in claim 1, characterized in that: Both the vertical HR end face (4) and the oblique HR end face (5) are coated with HR optical film.

5. The vertical-plane emitting laser array based on multi-unit, multi-grating, multi-wavelength, ultra-narrow linewidth as described in claim 1, characterized in that: The upper surface composite functional grating (33) is any one of the following: a surface-reflective metal comb grating, a semiconductor / SiO2 etched grating with a reflective optical film deposited on the upper surface, and a vapor-deposited planar metal comb grating.

6. The vertical-plane emitting laser array based on multi-unit, multi-grating, multi-wavelength, ultra-narrow linewidth laser according to claim 1, characterized in that: The resonant structure of the spine semiconductor laser (1) is a quasi-resonant cavity formed by the vertical HR end face (4) and the upper end face composite functional grating (33); by means of the reflection wavelength selection characteristics of the first-order filter grating (332), the resonant cavity has narrow linewidth optical quality characteristics.

7. The vertical-plane emitting laser array based on multi-unit, multi-grating, multi-wavelength, ultra-narrow linewidth laser according to claim 1, characterized in that: The grating constant of the second-order grating (331) in the same spine semiconductor laser (1) is twice the grating constant of the first-order filter grating (332).

8. The vertical-plane emitting laser array based on multi-unit, multi-grating, multi-wavelength, ultra-narrow linewidth laser according to claim 1, characterized in that, By adjusting the grating constant Λ of each unit (N,M) This enables each of the spine semiconductor lasers (1) in the array to output a specific wavelength that conforms to the ITU-T standard wavelength spacing, thereby achieving the multi-wavelength integration required for high-density wavelength division multiplexing.

9. The vertical-plane emitting laser array based on multi-unit, multi-grating, multi-wavelength, ultra-narrow linewidth laser according to claim 1, characterized in that: The upper surface composite functional grating (33) is an arbitrary grating, and its filtering function satisfies the λ of BRAGG. (N,M) / 2 grating constant; the material of the upper surface composite functional grating (33) is metal, semiconductor, dielectric, lithium niobate, piezoelectric ceramic or plastic; the type of the upper surface composite functional grating (33) is high reflectivity, transmission refraction or semi-transmission semi-reflection.

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