A photonic crystal surface emitting laser epitaxial structure with a bimodal mode field distribution
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-10
- Publication Date
- 2026-08-11
AI Technical Summary
然而，上述单峰模场分布下，有源层和光子晶体层的光限制因子仍有进一步优化的空间
[0029]1、本发明通过在光子晶体层上方引入折射率更高的GaAs调控层，使光子晶体层与其上下层形成高低高的折射率分布，将传统外延结构基模场的单峰分布优化为双峰分布，使得有源层和光子晶体层分别落入基模场的双峰内，从而有效提高了有源层和光子晶体层的光限制因子，进而使器件具有更高的电光转换效率，提升斜率效率。
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Figure CN122552937A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor laser technology, specifically relating to an epitaxial structure for a photonic crystal surface-emitting laser with a dual-peak mode field distribution. Background Technology
[0002] With the rapid development of laser processing, optical communication, and lidar applications, the industry's demand for single-mode, high-brightness semiconductor lasers is becoming increasingly urgent. However, traditional edge-emitting lasers and vertical-cavity surface-emitting lasers are limited by the multimode oscillations introduced by the increase in gain region size, making it difficult to maintain single-mode operation at high power. To solve this bottleneck, photonic crystal surface-emitting lasers have emerged. These devices utilize the two-dimensional standing-wave resonance effect of the photonic crystal bandgap to achieve large-area coherent lasing and vertical surface emission, thus possessing outstanding advantages such as high power, fundamental transverse mode operation, extremely narrow divergence angle, and excellent beam quality.
[0003] In the epitaxial structure of GaAs-based PCSELs, the PC layer is adjacent to the active layer, allowing light generated by the active layer to enter the PC layer via evanescent wave coupling. The active layer typically employs a quantum well structure, providing transversely polarized optical gain based on interband transition mechanisms. Considering the epitaxial structure of PCSELs as a multilayer optical waveguide, the optical confinement factor of the active layer determines the gain strength of the laser mode, while the optical confinement factor of the PC layer determines the strength of the evanescent wave coupling. Therefore, simultaneously improving the optical confinement factors of both the active and PC layers is crucial for enhancing device performance.
[0004] In existing technologies, the waveguide mode field design of PCSEL epitaxial structures is a single-peak distribution. However, under the aforementioned single-peak mode field distribution, there is still room for further optimization of the optical confinement factor of the active layer and the photonic crystal layer. To address the above problems, this invention proposes a photonic crystal surface-emitting laser epitaxial structure with a dual-peak mode field distribution. Summary of the Invention
[0005] To address the aforementioned problems in the prior art, the present invention aims to provide an epitaxial structure for a photonic crystal surface-emitting laser with a dual-peak mode field distribution.
[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:
[0007] An epitaxial structure for a photonic crystal surface-emitting laser with a bimodal mode field distribution includes:
[0008] Substrate;
[0009] An N-type cladding layer located on the substrate;
[0010] Active layer located on N-type cladding;
[0011] A photonic crystal layer located on the active layer;
[0012] A GaAs control layer located above the photonic crystal layer;
[0013] And, the P-type cladding layer located above the GaAs control layer;
[0014] Wherein, the refractive index of the GaAs control layer is higher than the equivalent refractive index of the photonic crystal layer, and there is an unetched GaAs layer below the photonic crystal layer with a refractive index higher than the equivalent refractive index of the photonic crystal layer, so that the photonic crystal layer and its upper and lower layers form a high-low-high refractive index distribution.
[0015] The high-low-high refractive index distribution causes the mode field distribution to exhibit two peaks, and the active layer and the photonic crystal layer are located within the two peaks respectively.
[0016] Preferably, it further includes:
[0017] The first waveguide layer is located between the N-type cladding and the active layer;
[0018] The second waveguide layer is located between the active layer and the photonic crystal layer;
[0019] Both the first waveguide layer and the second waveguide layer are AlGaAs layers.
[0020] Preferably, the GaAs control layer has a thickness of 121 nm, is made of GaAs, is p-type doped, and has a doping concentration of 5 × 10⁻⁶. 17 cm -3 Its refractive index is 3.55.
[0021] Preferably, the photonic crystal layer is a periodic structure formed by etching air holes on GaAs material, with an etching depth of 160 nm, a square lattice type, a lattice constant of 273 nm, and a dual-hole structure of ellipse and circle. The minor axis of the elliptical hole is 30 nm, the major axis is 72 nm, the radius of the circular hole is 25 nm, the X / Y spacing between the two holes is 70 nm, the duty cycle is 11.74%, and the equivalent refractive index is 3.37.
[0022] Preferably, the thickness of the unetched GaAs layer is 219 nm, the material is GaAs, the doping type is P-type, and the doping concentration is 5 × 10⁻⁶. 17 cm -3 Its refractive index is 3.55.
[0023] Preferably, the first waveguide layer is Al. X Ga 1-X As, where 0.05≤x≤0.75, thickness is 30nm, and refractive index range is 3.50-3.11; the second waveguide layer is Al. Y Ga 1-YAs, where 0.05≤y≤0.2, thickness is 30nm, and refractive index range is 3.50-3.42.
[0024] Preferably, the active layer is a multilayer quantum well structure composed of InGaAs and GaAs, with a well layer thickness of 7 nm, a barrier layer thickness of 10 nm, a period number of 3, a well layer refractive index of 3.58, and a barrier layer refractive index of 3.55.
[0025] Preferably, the system further includes a barrier layer located between the active layer and the first waveguide layer, wherein the barrier layer is made of GaAs, has a thickness of 10 nm, and a refractive index of 3.55.
[0026] Preferably, the N-type cladding is Al. 0.75 GaAs with a thickness of 1600 nm, N-type doped with a doping concentration of 1×10⁻⁶. 17 cm -3 The refractive index is 3.11; the P-type cladding is Al. 0.75 GaAs with a thickness of 1750 nm, P-type doping, and a doping concentration of 5 × 10⁻⁶. 17 cm -3 Up to 2×10 18 cm -3 Its refractive index is 3.11.
[0027] Preferably, the substrate is GaAs with a refractive index of 3.55.
[0028] Beneficial effects
[0029] 1. This invention introduces a GaAs control layer with a higher refractive index above the photonic crystal layer, so that the photonic crystal layer and the layers above and below it form a high-low refractive index distribution. This optimizes the single-peak distribution of the fundamental mode field of the traditional epitaxial structure into a double-peak distribution, so that the active layer and the photonic crystal layer fall into the double peaks of the fundamental mode field, thereby effectively improving the optical confinement factor of the active layer and the photonic crystal layer, and thus enabling the device to have higher electro-optical conversion efficiency and improved slope efficiency.
[0030] 2. In this invention, when the thickness of the GaAs control layer is 121 nm, the light confinement factor of the active layer is increased from 6.07% in the traditional structure to 6.89%, an increase of 0.82%; the light confinement factor of the photonic crystal layer is increased from 12.5% in the traditional structure to 19.8%, an increase of 7.3%. Attached Figure Description
[0031] Figure 1 The diagrams show the epitaxial structure of a traditional photonic crystal surface-emitting laser and the epitaxial structure of this invention with the addition of a GaAs control layer; wherein... Figure 1 (a) in the text represents a traditional extensional structure. Figure 1(b) in the figure represents the epitaxial structure after the addition of the GaAs control layer in this invention;
[0032] Figure 2 This is a structural diagram of the photonic crystal cell of the photonic crystal surface-emitting laser used in this invention;
[0033] Figure 3 The diagram illustrates the fundamental mode field distribution of a traditional photonic crystal surface-emitting laser and the fundamental mode field distribution after adding a GaAs modulation layer according to this invention; wherein... Figure 3 In the diagram, (a) shows the unimodal mode field distribution of the traditional structure. Figure 3 (b) in the figure represents the optimized bimodal mode field distribution of this invention;
[0034] Figure 4 This is a schematic diagram illustrating the variation of the light confinement factor of the active layer and photonic crystal layer with the thickness of the GaAs control layer in this invention. Detailed Implementation
[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely for explaining the invention and are not intended to limit the scope of protection of the invention.
[0036] This embodiment provides a photonic crystal surface-emitting laser epitaxial structure with a dual-peak mode field distribution. By introducing a GaAs control layer with a higher refractive index above the photonic crystal layer, the photonic crystal layer and its upper and lower layers form a high-low refractive index distribution, thereby causing the mode field distribution to exhibit two peaks. The active layer and the photonic crystal layer are located in the two peaks respectively, thereby simultaneously improving the light confinement factor of the active layer and the photonic crystal layer.
[0037] See Figure 1 As shown in (b), looking from bottom to top, the bottom layer is a GaAs substrate with a refractive index of 3.55. An N-type cladding layer is provided on the substrate, which is composed of Al... 0.75 It is composed of GaAs, with a thickness of 1600 nm and an N-type doping concentration of 1×10⁻⁶. 17 cm -3 The refractive index is 3.11. Above the N-type cladding is the first waveguide layer (located between the N-type cladding and the active layer), made of Al. X Ga 1-XThe active layer, made of InGaAs (aluminum composition x between 0.05 and 0.75), is 30 nm thick and has a refractive index varying between 3.50 and 3.11. It employs an InGaAs / GaAs multilayer quantum well structure, with a 7 nm well layer and a 10 nm barrier layer, spanning three periods. The well layer has a refractive index of 3.58, and the barrier layer has a refractive index of 3.55. Below the active layer is a 10 nm thick GaAs barrier layer with a refractive index of 3.55. Above the active layer is a second waveguide layer (located between the active layer and the unetched GaAs layer), made of Al. Y Ga 1-Y As (aluminum content y between 0.05 and 0.2), thickness 30 nm, refractive index between 3.50 and 3.42.
[0038] Immediately following the second waveguide layer is an unetched GaAs layer, 219 nm thick, with a p-type doping concentration of 5 × 10⁻⁶. 17 cm -3 , refractive index 3.55.
[0039] Above that is the photonic crystal layer, which is a periodic structure formed by etching air holes in GaAs material (see [link to cell configuration]). Figure 2 The etching depth of this layer is 160 nm, the lattice type is square, the lattice constant is 273 nm, and it adopts a dual-hole structure of elliptical and circular holes: the minor axis of the elliptical hole is 30 nm, the major axis is 72 nm, the radius of the circular hole is 25 nm, the spacing between the two holes in the X / Y directions is 70 nm, and the duty cycle is 11.74%. Based on this, the calculated equivalent refractive index is 3.37, and this layer is p-type doped with a concentration of 5 × 10⁻⁶. 17 cm -3 Above the photonic crystal layer is the key GaAs control layer of this invention, with a thickness of 121 nm and a p-type doping concentration of 5 × 10⁻⁶. 17 cm -3 The refractive index is 3.55. The top layer is a P-type cladding made of Al. 0.75 GaAs, 1750 nm thick, with a p-type doping concentration of 5 × 10⁻⁶ 17 cm -3 Up to 2×10 18 cm -3 Between these values, the refractive index is 3.11.
[0040] The equivalent refractive index of the photonic crystal layer (3.37) is lower than that of the unetched GaAs layer below it (3.55) and the GaAs modulated layer above it (3.55). Therefore, the photonic crystal layer and its surrounding layers form a "high-low-high" refractive index distribution, meaning the refractive indices of the upper and lower layers are higher than those of the intermediate layer. Simulation calculations using the intrinsic mode solver, such as... Figure 3As shown in (b), this refractive index distribution results in two peaks in the mode field distribution within the epitaxial structure. The active layer falls within the lower peak, while the photonic crystal layer falls within the upper peak. In contrast, the traditional structure without a GaAs modulation layer ( Figure 1 (a) in the middle only produces a unimodal distribution. Figure 3 (a) in the example cannot simultaneously provide a high confinement factor for both the active layer and the photonic crystal layer.
[0041] Furthermore, to optimize device performance, this invention utilizes an intrinsic mode solver to perform sweep optimization on the thickness of the GaAs control layer. The constraint factor is defined as follows:
[0042]
[0043] In the formula: and Z represents the confinement factor of the active layer and the photonic crystal layer, respectively; Z represents the vertical position of the epitaxial structure; E(z) represents the normalized electric field distribution in the vertical direction. This represents the integral over the entire epitaxial waveguide structure; and These represent the integrals over the active layer and the photonic crystal layer, respectively.
[0044] like Figure 4 As shown, with increasing GaAs modulation layer thickness, the confinement factor of the active layer first increases and then decreases, while the confinement factor of the photonic crystal layer increases monotonically. When the modulation layer thickness is 0 (i.e., the conventional structure), the confinement factors of the active layer and the photonic crystal layer are 6.07% and 12.5%, respectively. When the thickness reaches 121 nm, the confinement factor of the active layer rises to its maximum value of 6.89%, while the confinement factor of the photonic crystal layer increases to 19.8%. Compared with the conventional structure, the confinement factor of the active layer increases by 0.82 percentage points, and the confinement factor of the photonic crystal layer increases by 7.3 percentage points. Higher confinement factors mean stronger optical gain and more efficient evanescent wave coupling, thus enabling the device to achieve higher electro-optical conversion efficiency and slope efficiency.
[0045] In summary, the epitaxial structure proposed in this invention achieves a bimodal mode field distribution through the above-mentioned refractive index profile design, which significantly improves the light confinement factor of the active layer and the photonic crystal layer.
[0046] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. An epitaxial structure for a photonic crystal surface-emitting laser with a bimodal mode field distribution, characterized in that, include: Substrate; An N-type cladding layer located on the substrate; Active layer located on N-type cladding; A photonic crystal layer located on the active layer; A GaAs control layer located above the photonic crystal layer; And, the P-type cladding layer located above the GaAs control layer; Wherein, the refractive index of the GaAs control layer is higher than the equivalent refractive index of the photonic crystal layer, and there is an unetched GaAs layer below the photonic crystal layer with a refractive index higher than the equivalent refractive index of the photonic crystal layer, so that the photonic crystal layer and its upper and lower layers form a high-low-high refractive index distribution. The high-low-high refractive index distribution causes the mode field distribution to exhibit two peaks, and the active layer and the photonic crystal layer are located within the two peaks respectively.
2. The epitaxial structure of a photonic crystal surface-emitting laser with a dual-peak mode field distribution according to claim 1, characterized in that, Also includes: The first waveguide layer is located between the N-type cladding and the active layer; The second waveguide layer is located between the active layer and the photonic crystal layer; Both the first waveguide layer and the second waveguide layer are AlGaAs layers.
3. The epitaxial structure of a photonic crystal surface-emitting laser with a dual-peak mode field distribution according to claim 1, characterized in that, The GaAs control layer has a thickness of 121 nm, is made of GaAs, is p-type doped, and has a doping concentration of 5 × 10⁻⁶. 17 cm -3 Its refractive index is 3.
55.
4. The epitaxial structure of a photonic crystal surface-emitting laser with a dual-peak mode field distribution according to claim 1, characterized in that, The photonic crystal layer is a periodic structure formed by etching air holes on GaAs material. The etching depth is 160 nm, the lattice type is a square lattice, the lattice constant is 273 nm, and a dual-hole structure of ellipse and circle is adopted. The minor axis of the elliptical hole is 30 nm, the major axis is 72 nm, the radius of the circular hole is 25 nm, the X / Y direction spacing of the dual holes is 70 nm, the duty cycle is 11.74%, and the equivalent refractive index is 3.
37.
5. The epitaxial structure of a photonic crystal surface-emitting laser with a dual-peak mode field distribution according to claim 1, characterized in that, The unetched GaAs layer has a thickness of 219 nm, is made of GaAs, is p-type doped, and has a doping concentration of 5 × 10⁻⁶. 17 cm -3 Its refractive index is 3.
55.
6. The epitaxial structure of a photonic crystal surface-emitting laser with a bimodal mode field distribution according to claim 2, characterized in that, The first waveguide layer is Al X Ga 1-X As, where 0.05≤x≤0.75, thickness is 30nm, and refractive index ranges from 3.50 to 3.11; the second waveguide layer is Al. Y Ga 1-Y As, where 0.05≤y≤0.2, thickness is 30nm, and refractive index range is 3.50-3.
42.
7. The epitaxial structure of a photonic crystal surface-emitting laser with a bimodal mode field distribution according to claim 1, characterized in that, The active layer is a multilayer quantum well structure composed of InGaAs and GaAs, with a well layer thickness of 7 nm, a barrier layer thickness of 10 nm, a period number of 3, a well layer refractive index of 3.58, and a barrier layer refractive index of 3.
55.
8. The epitaxial structure of a photonic crystal surface-emitting laser with a bimodal mode field distribution according to claim 2, characterized in that, It also includes a barrier layer located between the active layer and the first waveguide layer, the barrier layer being made of GaAs with a thickness of 10 nm and a refractive index of 3.
55.
9. The epitaxial structure of a photonic crystal surface-emitting laser with a bimodal mode field distribution according to claim 1, characterized in that, The N-type cladding is Al. 0.75 GaAs with a thickness of 1600 nm, N-type doped with a doping concentration of 1×10⁻⁶. 17 cm -3 The refractive index is 3.11; the P-type cladding is Al. 0.75 GaAs with a thickness of 1750 nm, P-type doping, and a doping concentration of 5 × 10⁻⁶. 17 cm -3 Up to 2×10 18 cm -3 Its refractive index is 3.
11.
10. The epitaxial structure of a photonic crystal surface-emitting laser with a dual-peak mode field distribution according to claim 1, characterized in that, The substrate is GaAs with a refractive index of 3.55.