High-power single-mode laser structure based on multiple photon filtering layers

Abstract

The invention relates to the technical field of vertical cavity surface emitting lasers, in particular to a high-power single-mode laser structure based on multiple photon filtering layers, which comprises a substrate layer, a DBR (distributed bragg reflector) is arranged on the substrate layer, and an active area is embedded in the DBR; a plurality of photon filtering layers are embedded in the DBR, and the photon filtering layers are in integrated distribution of a central low-refractive-index area and a peripheral high-refractive-index area in the transverse direction, so that high-side-mode-rejection-ratio single-mode output under a large aperture is realized; a plurality of large-aperture oxidation limiting layers are embedded in the DBR and used for limiting a current injection area and improving the electric heating performance of the device. According to the VCSEL device, high side mode rejection ratio, high-power single-mode output and excellent thermal stability can be achieved under the working condition of room-temperature continuous waves, the whole manufacturing process is simple and controllable, repeatability is high, and the VCSEL device is suitable for large-scale manufacturing.

Description

Technical Field

[0001] This invention relates to the field of vertical cavity surface-emitting laser technology, and in particular to a high-power single-mode laser structure based on a multilayer photonic filter layer. Background Technology

[0002] Vertical-cavity surface-emitting semiconductor lasers (VCSELs) have become the mainstream light source in short-distance optical interconnects, fiber coupling, 3D sensing / imaging, LiDAR, and high-density optical interconnects due to their advantages such as short longitudinal cavity length, near-circular near-field spot size, low divergence angle, and ease of two-dimensional arraying. Their typical structure consists of vertically distributed Bragg mirrors (DBRs) and an active region. The DBRs achieve high reflectivity through a stack of high and low refractive index materials, ensuring longitudinal resonance and low threshold emission.

[0003] In terms of lateral single-mode control, existing technologies mainly include three mechanisms: oxide aperture, ion / proton implantation, and relief structure / grating. Among them, oxide aperture technology is widely used due to its mature process and ease of mass production. However, it effectively blocks higher-order lateral modes, requiring the oxide aperture to be reduced to the micrometer level (e.g., ≤5μm). This leads to a significant increase in device differential resistance and thermal resistance, and a rise in junction temperature, thus limiting output power and long-term reliability. To balance large aperture and single-mode performance, existing technologies attempt to combine optical selective filtering or phase engineering with traditional oxide aperture, suppressing higher-order modes through intracavity interference or mode defect differences to achieve high-power single-mode output. However, how to achieve single-mode output of VCSELs with a relatively large effective emission aperture, while simultaneously solving the problems of aperture reduction, increased resistance, and poor heat dissipation, remains a core technical challenge that urgently needs to be addressed in this field.

[0004] Therefore, this invention discloses a high-power single-mode laser structure based on a multilayer photonic filter layer to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a high-power single-mode laser structure based on a multilayer photonic filter layer to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: The present invention provides a high-power single-mode laser structure based on a multilayer photonic filter layer, including a substrate layer, wherein a DBR is disposed on the substrate layer, and an active region is embedded in the DBR;

[0007] The DBR is embedded with several photon filter layers. The photon filter layers are arranged in an integrated manner with a central low refractive index region and a peripheral high refractive index region in the lateral direction, so as to achieve high side-mode suppression ratio single-mode output under large aperture.

[0008] The DBR has several large-pore oxide confinement layers embedded in it to limit the current injection area and improve the electrothermal performance of the device, while also helping to achieve high power output.

[0009] Preferably, the photonic filter layer is prepared using a combined wet oxidation and secondary epitaxial process. During preparation, a low-refractive-index central region is first formed within a defined area through wet oxidation, and then a high-refractive-index material is selectively regrown around the periphery to construct a ring-shaped peripheral high-refractive-index region, forming an optically constrained region with radial refractive index distribution.

[0010] Preferably, the refractive index of the low refractive index central region is n=1.5-1.7, and the diameter is 2-11μm; the refractive index of the peripheral high refractive index region is n=3.4-3.6.

[0011] Preferably, the DBR includes a lower N-type DBR and an upper P-type DBR arranged vertically from bottom to top, and the active region is disposed between the lower N-type DBR and the upper P-type DBR.

[0012] Preferably, the multilayer photonic filter layer is arranged in the upper P-type DBR or the lower N-type DBR, or it can be arranged simultaneously in the lower N-type DBR and the upper P-type DBR.

[0013] Preferably, the substrate layer comprises a p-type semi-insulating GaAs or Si-based material.

[0014] Preferably, the DBR comprises alternating stacks of Al x Ga 1₋x As / GaAs or AlGa 1₋ As / GaAs dielectric layer.

[0015] Preferably, a positive electrode is disposed on the upper P-type DBR, and a negative electrode is disposed on the substrate layer.

[0016] Preferably, the outer walls of the lower N-type DBR and the upper P-type DBR are surrounded by a surface passivation layer.

[0017] Preferably, the high-power single-mode laser structure based on a multi-layer photonic filter layer is fabricated as a multi-mesa small array layout, and multiple mesa units are interconnected by metal to achieve unified current injection.

[0018] Compared with existing technologies, this invention has the following advantages and technical effects: This invention discloses a high-power single-mode laser structure based on a multilayer photonic filter layer. Through the synergistic design of a large-aperture oxide confinement layer and a multilayer photonic filter layer, it effectively suppresses the disordered diffusion of the transverse optical field and significantly enhances the single-transverse mode dominance, thereby improving the stability of single-mode output and the side-mode suppression ratio. This structure avoids reliance on complex surface etching or additional microstructure processing, making the process flow simpler and easier to scale up. At the same time, the larger effective emission aperture significantly reduces the device's differential resistance and junction temperature, which is beneficial to improving the device's maximum continuous wave output power and thermal stability. In addition, this structure uses a multi-mesa small array, which can maintain single-mode characteristics while increasing the overall emission area and heat dissipation channels. Through reasonable current distribution and interconnection design, power multiplication is achieved without sacrificing single-mode stability, thereby improving the device's reliability and process yield.

[0019] The VCSEL device of the present invention can achieve high side-mode rejection ratio, high power single-mode output and excellent thermal stability under continuous wave operation at room temperature. Furthermore, the entire manufacturing process is simple, controllable and highly repeatable, making it suitable for large-scale manufacturing. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0021] Figure 1 This is a cross-sectional view of the high-power single-mode laser structure based on a multilayer photonic filter layer according to the present invention;

[0022] Figure 2 This is a top view schematic diagram of the multi-platform array structure of the present invention;

[0023] In the figure: 100, positive electrode; 200, oxide confinement layer; 300, surface passivation layer; 400, photon filter layer; 500, substrate layer; 600, negative electrode; 700, active region; 800, upper P-type DBR; 900, lower N-type DBR. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Reference Figures 1 to 2 As shown, this embodiment provides a high-power single-mode laser structure based on a multilayer photonic filter layer, including a substrate layer 500, a DBR disposed on the substrate layer 500, and an active region 700 embedded in the DBR.

[0027] The DBR has several photon filter layers 400 embedded in it. The photon filter layers 400 have an integrated distribution of a central low refractive index region and a peripheral high refractive index region in the lateral direction, which realizes a single-mode output with a high side-mode suppression ratio under a large aperture.

[0028] The DBR incorporates several large-aperture oxide confinement layers 200 to define the current injection region and improve the device's electrothermal performance, while also helping to achieve high power output.

[0029] This invention discloses a high-power single-mode laser structure based on a multilayer photonic filter. Through the synergistic design of a large-aperture oxide confinement layer 200 and a multilayer photonic filter layer 400, the disordered diffusion of the transverse optical field is effectively suppressed and the fundamental transverse mode dominance is significantly enhanced, thereby improving the stability of single-mode output and the side-mode suppression ratio. This structure avoids reliance on complex surface etching or additional microstructure processing, resulting in a simpler process flow and easier process scale-up. At the same time, the larger effective emission aperture significantly reduces the device's differential resistance and junction temperature, which is beneficial for improving the device's maximum continuous wave output power and thermal stability. Furthermore, this structure employs a multi-mesa small array, which can maintain single-mode characteristics while increasing the overall emission area and heat dissipation channels. Through reasonable current distribution and interconnection design, power multiplication is achieved without sacrificing single-mode stability, thereby improving device reliability and process yield.

[0030] Further optimizing the design, the photonic filter layer 400 is fabricated using a combination of wet oxidation and secondary epitaxy. During fabrication, a low-refractive-index central region is first formed within a defined area through wet oxidation. Then, a high-refractive-index material is selectively grown around the periphery to construct a ring-shaped peripheral high-refractive-index region, forming an optically constrained region with radial refractive index distribution. The photonic filter layer 400 is a multilayer radial filter unit embedded within the DBR. Employing a combination of wet oxidation and secondary epitaxy, it exhibits an integrated distribution of a central low-refractive-index region and a peripheral high-refractive-index region laterally. The optical thickness of each layer is designed as a non-standard thickness, deviating from the traditional λ / 4 condition, thus forming an optically constrained region with radial refractive index distribution. This enables selective filtering of transverse modes and effective suppression of higher-order modes, improving the stability of single-mode output.

[0031] In one embodiment of the present invention, the photonic filter layer 400 operates based on the interference effect. By introducing a dielectric layer structure with a thickness other than λ / 4 inside the DBR, the phase accumulation of different transverse modes propagating in this structure is controlled. This allows the fundamental mode to satisfy constructive interference at the designed wavelength and maintain high reflectivity, while certain higher-order modes, due to the disruption of phase conditions, exhibit destructive interference, resulting in a significant decrease in reflectivity or an increase in transmission / leakage. In other words, the photonic filter layer 400 optically "filters out" higher-order modes through the interference principle, making it difficult for them to reach the oscillation condition when longitudinal feedback is insufficient, while the fundamental mode still has sufficient feedback to maintain stable oscillation, thereby achieving high side-mode suppression ratio single-mode output under large aperture conditions.

[0032] Further optimization of the scheme resulted in a refractive index of n = 1.5-1.7 and a diameter of 2-11 μm for the low-refractive-index central region, and a refractive index of n = 3.4-3.6 for the peripheral high-refractive-index region. In the actual fabrication process, the refractive index of the central low-refractive-index region was approximately n ≈ 1.6, with a diameter of 2-11 μm, while the refractive index of the peripheral high-refractive-index region was approximately n ≈ 3.5.

[0033] In one embodiment of the present invention, the low refractive index region at the center of the photon filter layer 400 may be oxidized AlO. 98 Ga0. 02 As, the outer high refractive index region can be composed of GaAs or low aluminum composition AlGaAs, used to form a high refractive index annular optical confinement region.

[0034] In one embodiment of the present invention, the oxidation confinement layer 200 has a large oxidation pore size at its center, and the unoxidized pore size at its center is >10μm.

[0035] In one embodiment of the present invention, the oxide confinement layer 200 and the photonic filter layer 400 are designed synergistically, complementing each other functionally: the oxide confinement layer 200 is mainly responsible for the lateral confinement of current injection and provides a basic lateral refractive index step to reduce series resistance and improve thermal resistance characteristics; the photonic filter layer 400 selectively weakens the longitudinal feedback of higher-order modes using the interference principle, and further increases its lateral leakage channels with the help of the radial structure. Under their synergistic effect, the large-aperture oxide confinement layer 200 ensures the electrothermal stability of the device at high power, while the photonic filter layer 400 filters out higher-order modes at the optical level, thereby achieving dual suppression of higher-order modes while maintaining the large-aperture, low-resistance, and high heat dissipation conditions, ensuring that the fundamental mode is steadily dominant in gain competition.

[0036] Further optimization of the design reveals that the DBR comprises a lower N-type DBR900 and an upper P-type DBR800 arranged vertically from bottom to top, with the active region 700 positioned between them. The lower N-type DBR900, active region 700, and upper P-type DBR800 are arranged vertically from bottom to top on the substrate layer 500, forming the basis for the vertical cavity surface-emitting laser to achieve longitudinal resonance and low-threshold emission, providing essential conditions for the normal operation of the device.

[0037] Further optimization involves placing the multilayer photonic filter layer 400 within either the upper P-type DBR800 or the lower N-type DBR900, or simultaneously within both the lower N-type DBR900 and the upper P-type DBR800. This flexible arrangement of the photonic filter layer 400 within the DBR ensures that only a single mode achieves high reflectivity at the designed wavelength, while specific higher-order transverse modes are effectively suppressed, thereby achieving mode-selective control and improving single-mode output power.

[0038] In one embodiment of the present invention, the photonic filter layer 400 is inserted above the 6th and 7th pairs of mirrors near the active region 700 of the upper P-type DBR 800, and each pair contains several high-refractive-index / low-refractive-index dielectric layers with non-standard optical thicknesses. This structure is equivalent to embedding a selective reflection filter within the mirror, which can change the reflection characteristics of different transverse modes.

[0039] Further optimization involves a substrate layer 500 comprising a p-type semi-insulating GaAs or Si-based material. The p-type semi-insulating GaAs or Si-based material meets the device's manufacturing and performance requirements, ensuring its stability and reliability.

[0040] Further optimization of the scheme, DBR includes alternating stacked Al x Ga 1₋x As / GaAs or AlGa 1₋ The alternating stacking of As / GaAs dielectric layers enables high reflectivity in the DBR, ensuring longitudinal resonance conditions and low threshold emission, thus providing a foundation for high-power single-mode output and achieving high reflectivity.

[0041] In one embodiment of the present invention, the active region 700 is generally composed of several pairs of quantum wells and a stress compensation layer.

[0042] In one embodiment of the present invention, the oxide confinement layer 200 is formed by wet oxidation of a high-alumina component AlGaAs to create a current-limiting hole; the high-alumina component AlGaAs is such as AlAs or AlO. 98 Ga0. 02 As.

[0043] To further optimize the design, a positive electrode 100 is provided on the upper P-type DBR800, and a negative electrode 600 is provided on the substrate layer 500. The positive electrode 100 is located at the top of the upper P-type DBR800, while the negative electrode 600 is located on the substrate layer 500, which facilitates current injection, provides power support for the normal operation of the device, and ensures that the device can stably emit laser light.

[0044] In one embodiment of the present invention, the positive electrode 100 and the light-emitting area of ​​the top layer adopt a multi-mesa small array layout. Multiple mesa units achieve uniform current injection and a larger overall light-emitting area through reasonable metal interconnection, significantly improving the device's output power and heat dissipation capacity while maintaining the single-mode emission characteristics of each unit. The optimized current distribution and interconnection design avoid resistance unevenness or thermal degradation caused by the array structure, ensuring that the photoelectric conversion efficiency of a single mesa remains essentially unaffected.

[0045] In one embodiment of the present invention, by fabricating the device as an array of multiple small-diameter mesa, each unit maintains single-mode characteristics, and the multiple mesa are interconnected to achieve uniform current injection and overall light emission, while increasing the light emission area and heat dissipation capacity, the high-order modes that are prone to occur in large-aperture devices are avoided, thereby achieving high-power stable output under single-mode conditions.

[0046] In one embodiment of the present invention, the VCSEL device fabricated using the above-described structure can achieve high side-mode rejection ratio, high-power single-mode output and excellent thermal stability under continuous wave operation at room temperature. Furthermore, the entire fabrication process is simple, controllable, and highly repeatable, making it suitable for large-scale manufacturing.

[0047] In a further optimized design, the outer walls of the lower N-type DBR900 and the upper P-type DBR800 are surrounded by a surface passivation layer 300. The surface passivation layer 300 protects the device surface, reduces the impact of surface states on device performance, and improves the reliability and stability of the device.

[0048] Further optimization of the scheme led to the fabrication of a high-power single-mode laser structure based on a multi-layer photonic filter layer, arranged in a multi-mesa array. Multiple mesa units are interconnected by metal to achieve uniform current injection. This optimized metal interconnection ensures uniform current injection and a larger overall emitting area, significantly improving device output power and heat dissipation while maintaining the single-mode emission characteristics of each unit. The optimized current distribution and interconnection design avoid resistance unevenness or thermal degradation caused by the array structure, ensuring that the photoelectric conversion efficiency of a single mesa remains largely unaffected.

[0049] Preparation process:

[0050] Primary epitaxial growth: The lower DBR, active region 700, and part of the upper DBR are sequentially epitaxially grown on a GaAs substrate using MOCVD or MBE. A high-aluminum Al content is reserved in the upper DBR near the active region 700. x Ga 1₋x An As (x≈0.98) layer serves as the oxidation confinement layer 200 for subsequent wet oxidation. A thin protective layer may be applied to the surface if necessary to facilitate subsequent etching processes.

[0051] Etching oxidation channel: Through photolithography and etching processes, a circular opening is formed on the top layer of the device, and the etching depth is controlled to the edge of the oxide confinement layer 200, thereby providing an effective lateral oxygen inlet channel for wet oxidation.

[0052] Wet oxidation and formation of photon filter layer 400: Al oxidation at 350–420°C x Ga 1₋x The As layer undergoes wet oxidation to form a low-refractive-index oxide circle region with n≈1.6. Subsequently, high-refractive-index materials such as GaAs or low-aluminum AlGaAs are selectively regrown around the oxide circle to construct a ring-shaped high-refractive-index layer with n≈3.5, thereby forming a photon filter layer 400 with a radial refractive index distribution.

[0053] Secondary epitaxy and DBR completion: After the photonic filter layer 400 is formed, the remaining upper DBR structure is epitaxially grown, and additional non-standard optical thickness layers can be introduced inside the DBR as needed to further optimize the reflection spectrum characteristics and mode selection performance.

[0054] Multi-mesa array fabrication: After completing the DBR, the device is fabricated into a multi-mesa array structure through photolithography and etching processes, and a unified current injection is achieved by using metal interconnects to expand the effective light-emitting area and heat dissipation channels, thereby improving output power and thermal stability.

[0055] Oxidation confinement layer 200 formation: The multi-mesa structure is subjected to wet oxidation treatment again to form current confinement holes at preset positions, so as to achieve uniform current injection and stable mode control.

[0056] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0057] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A high power single mode laser structure based on a multi-layer photonic filtering layer, characterized in that: The high-power single-mode laser structure based on the multi-layer photon filtering layer is prepared as a multi-mesa small array layout, and multiple mesa units are uniformly current-injected through metal interconnection. The DBR is embedded with a plurality of large-aperture oxidation confinement layers (200) for limiting current injection area and improving the electrical and thermal performance of the device, and also for helping to achieve high-power output. The photon filtering layer (400) is prepared by a wet oxidation and secondary epitaxial composite process, and during preparation, a low refractive index central region is first formed in a limited area by wet oxidation, and then a high refractive index material is selectively regrown in the periphery to build a ring-shaped high refractive index peripheral region, thereby forming a radially refractive index distributed optical confinement region.

2. The high power single mode laser structure based on a multi-layer photon filtering layer according to claim 1, characterized in that: The low refractive index central region has a refractive index of n=1.5-1.7 and a diameter of 2-11 μm; and the high refractive index peripheral region has a refractive index of n=3.4-3.

6.

3. The high power single mode laser structure based on a multi-layer photon filtering layer according to claim 2, characterized in that: The DBR includes a lower layer N-type DBR (900) and an upper layer P-type DBR (800) arranged vertically from bottom to top, and the active region (700) is arranged between the lower layer N-type DBR (900) and the upper layer P-type DBR (800).

4. The high power single mode laser structure based on a multi-layer photon filtering layer according to claim 1, characterized in that: The multi-layer photon filtering layer (400) is arranged in the upper layer P-type DBR (800) or the lower layer N-type DBR (900), or simultaneously arranged in the lower layer N-type DBR (900) and the upper layer P-type DBR (800).

5. The high power single mode laser structure based on a multi-layer photon filtering layer according to claim 4, characterized in that: The substrate layer (500) includes a P-type semi-insulating GaAs or Si-based material.

6. The high power single mode laser structure based on a multi-layer photon filtering layer according to claim 1, characterized in that: The upper layer P-type DBR (800) is provided with a positive electrode (100), and the substrate layer (500) is provided with a negative electrode (600).

7. The high power single mode laser structure based on a multi-layer photon filtering layer according to claim 1, characterized in that: The DBR includes an alternating stack of Al x Ga 1₋x As / GaAs or AlᵧGa 1₋ ᵧAs / GaAs dielectric layers.

8. The high power single mode laser structure based on a multi-layer photon filtering layer according to claim 4, characterized in that: The outer wall of the lower layer N-type DBR (900) and the upper layer P-type DBR (800) is surrounded by a surface passivation layer (300).

9. The high power single mode laser structure based on a multi-layer photon filtering layer according to claim 8, characterized in that: The high-power single-mode laser structure based on the multi-layer photon filtering layer is prepared as a multi-mesa small array layout, and multiple mesa units are uniformly current-injected through metal interconnection.

10. The high power single mode laser structure based on a multi-layer photon filtering layer according to claim 1, characterized in that: ​

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