Gain coupling type semiconductor laser based on current limiting layer in waveguide
By preparing an N-type doped current barrier layer in the P-type waveguide, the problem of complex process of gain-coupled DFB semiconductor laser and the problem of gain threshold reduction at high current is solved, and high-power single-mode laser and better device performance are achieved.
Patent Information
- Application Number
- CN202411462422.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-18
- Publication Date
- 2025-01-10
AI Technical Summary
The existing gain-coupled DFB semiconductor lasers have complex preparation processes. The comparison of the gain threshold value of the active layer is lowered under high injection current, making it difficult to achieve high-power single-mode lasers, and the single-mode characteristics deteriorate at high power.
A periodic N-type doped current barrier layer is prepared in the P-type waveguide, and the distributed limitation is achieved through the current barrier layer, increasing the carrier distribution contrast of the active layer, and improving the single longitudinal mode operating current range and power.
High-power single longitudinal mode laser is realized under high current conditions, which improves the single-mode laser performance of the gain-coupled DFB laser and enhances the stability and reliability of the device.
Smart Images
Figure CN119297735A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of semiconductor lasers, and in particular relates to a gain-coupled semiconductor laser based on a current limiting layer in a waveguide. Background Art
[0002] With the rapid development of technologies such as big data, cloud computing, quantum communication, 5G communication, and lidar, the performance requirements for lasers are constantly increasing, such as high power, narrow linewidth, tunability, high stability, high reliability, and high modulation rate. Semiconductor lasers with advantages such as small size, long service life, and high energy conversion efficiency are increasingly valued. Compared with FP cavity semiconductor lasers with wide linewidth and multi-longitudinal mode lasing, distributed feedback Bragg (DFB) semiconductor lasers with narrow linewidth, single longitudinal mode lasing, and direct modulation are becoming the core of various active devices. Compared with FP cavity semiconductor lasers, DFB semiconductor lasers add a grating layer above or below the active layer. The grating achieves resonance selection of a specific wavelength by periodically perturbing the physical parameters (refractive index or gain / loss) of the laser waveguide and active layer. Based on the different internal feedback mechanisms of the semiconductor, DFB semiconductor lasers can be divided into refractive index-coupled DFB semiconductor lasers and gain-coupled DFB semiconductor lasers. The refractive index-coupled DFB semiconductor laser mainly realizes laser lasing by periodically changing the refractive index and then periodically modulating the real part of the effective refractive index of the light field, while the gain-coupled DFB semiconductor laser realizes single longitudinal mode lasing by periodically modulating the imaginary part of the effective refractive index of the light field.
[0003] However, the refractive index-coupled DFB laser with uniform grating period has dual-mode lasing during operation, and its single-mode yield is low even if the end-face reflective film is introduced. Although stable single-mode lasing can be achieved by using a phase-shifted grating structure for mode selection, the single-mode characteristics deteriorate and the line width widens under high power due to the influence of spatial hole burning. The gain-coupled DFB semiconductor laser has the unique characteristic of the intrinsic mode with the lowest gain threshold, so it can stably lasing in single mode during operation without the need for mode selection.
[0004] At present, there are two methods to achieve gain-coupled DFB semiconductor lasers. The first method is to use micro-nanoscale grating preparation process and secondary epitaxial growth process to achieve gain coupling by directly etching gratings in the active layer or making non-absorption gratings near the active layer. However, nano-scale etching and secondary epitaxial processes are complex and the preparation cost is very high. Etching gratings near the active layer will also reduce the reliability and stability of the laser, which seriously limits the large-scale application of gain-coupled DFB semiconductor lasers. The second method is to periodically inject current into the active layer, so that the active layer periodically gains and achieves the effect of gain coupling. Although this method simplifies the process, due to the surface process being far away from the quantum well, the carrier concentration in the quantum well is not much different, and the gain difference is low. Therefore, the line width is wide during single longitudinal mode lasing, and as the injection current increases, the gain threshold contrast inside the active layer decreases under high injection current. After the quantum well is saturated, it presents a multi-mode working state, making it difficult to achieve high-power single-mode lasing. Summary of the invention
[0005] In view of the above technical problems, the present invention aims to provide a gain-coupled semiconductor laser based on a current limiting layer in a waveguide, which is characterized by preparing a periodic N-type doped current blocking layer in a P-type waveguide to achieve distributed current limitation. Compared with the surface structure, it can effectively improve the contrast of carrier distribution in the active layer, increase the gain contrast, increase the current range of single longitudinal mode operation, obtain a high-power single longitudinal mode device, and provide a new solution for achieving a gain-coupled DFB semiconductor laser with high-power stable single-mode output.
[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A gain-coupled semiconductor laser based on a current limiting layer in a waveguide comprises a substrate and an epitaxial structure grown on the substrate, wherein the epitaxial structure comprises a lower cladding layer, a lower waveguide layer, an active layer, an upper waveguide layer, a current blocking layer, a buried upper waveguide layer, an upper cladding layer, a cap layer and a diffusion blocking layer stacked in sequence from bottom to top, wherein the current blocking layer is a periodic structure and is buried in the buried upper waveguide layer, wherein the substrate, the lower cladding layer, the lower waveguide layer and the current blocking layer are N-type doped structures, and the upper waveguide layer, the buried upper waveguide layer, the upper cladding layer and the cap layer are P-type doped structures.
[0007] A gain-coupled semiconductor laser based on a current limiting layer in a waveguide comprises a substrate and an epitaxial structure grown on the substrate, wherein the epitaxial structure comprises a lower cladding layer, a lower waveguide layer, an active layer, an upper waveguide layer, a current blocking layer, a buried upper waveguide layer, an upper cladding layer and a cap layer stacked in sequence from bottom to top, wherein the upper waveguide layer is etched downward from the diffusion blocking layer to make the current blocking layer a periodic structure, and ion diffusion is performed in the exposed area after etching to form a diffusion area, wherein the substrate, the lower cladding layer, the lower waveguide layer and the current blocking layer are N-type doped structures, and the upper waveguide layer, the buried upper waveguide layer, the upper cladding layer and the cap layer are P-type doped structures.
[0008] Furthermore, the diffused ions are zinc ions, so as to prepare periodic current channels in the current blocking layer.
[0009] Compared with the prior art, the present invention can achieve the following beneficial effects: The present invention prepares an N-type doped current blocking layer in a P-type waveguide so that the active layer obtains periodic current injection. Since the current blocking layer can be prepared in a region very close to the active layer, compared with the surface structure, it is more capable of achieving periodic distribution of carriers in the active layer, thereby obtaining a high gain contrast in the active layer, and being able to maintain single longitudinal mode lasing under high current conditions. Its single longitudinal mode lasing operating current and power are higher than those of the surface structure, which can improve the maximum single longitudinal mode lasing power index of the gain-coupled DFB laser and obtain better device performance. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1-Figure 3 It is a schematic diagram of the preparation process of a gain-coupled semiconductor laser based on a current confinement layer in a waveguide provided in Example 1 of the present invention; Figure 4 and Figure 5 It is a schematic diagram of the preparation process of a gain-coupled semiconductor laser based on a current confinement layer in a waveguide provided in Example 2 of the present invention.
[0011] The reference numerals therein include: substrate 1, lower cladding layer 2, lower waveguide layer 3, active layer 4, upper waveguide layer 5, current blocking layer 6, buried upper waveguide layer 7, upper cladding layer 8, cap layer 9, diffusion region 10, and diffusion barrier layer 11. DETAILED DESCRIPTION
[0012] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.
[0013] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.
[0014] In order to solve the problem that the traditional gain-coupled DFB semiconductor laser has a complicated preparation process and the internal gain threshold contrast of the active layer is reduced under high injection current, and it is impossible to achieve stable high-power single longitudinal mode lasing under large current injection. The present invention innovatively proposes to use a periodic N-type doped current blocking layer prepared in a P-type waveguide to achieve distributed current limitation, thereby increasing the gain contrast of the active layer and achieving stable high-power single longitudinal mode lasing under large current injection.
[0015] Example 1 Figure 1-Figure 3 The preparation process of a gain-coupled semiconductor laser based on a current confinement layer in a waveguide according to Embodiment 1 of the present invention is shown.
[0016] like Figure 1-Figure 3 As shown, the gain-coupled semiconductor laser based on the current confinement layer in the waveguide provided by Embodiment 1 of the present invention includes a substrate 1 and an epitaxial structure grown on the substrate 1, wherein the epitaxial structure includes a lower cladding layer 2, a lower waveguide layer 3, an active layer 4, an upper waveguide layer 5, a current blocking layer 6, a buried upper waveguide layer 7, an upper cladding layer 8 and a cap layer 9 stacked in sequence from bottom to top, and the current blocking layer 6 is buried in the buried upper waveguide layer 7.
[0017] The preparation process of the gain-coupled semiconductor laser based on the current confinement layer in the waveguide of Example 1 is as follows: First, a lower cladding layer 2, a lower waveguide layer 3, an active layer 4, an upper waveguide layer 5 and a current blocking layer 6 are sequentially grown on a substrate 1 by MOCVD technology. Figure 1 Then, by photolithography and etching techniques, the current blocking layer 6 is prepared into a periodic structure, such as Figure 2 As shown, after that, the buried upper waveguide layer 7, the upper cladding layer 8 and the cap layer 9 are prepared by secondary epitaxial technology, and the buried upper waveguide layer 7 buries the current blocking layer 6; finally, the desired device is obtained by the general semiconductor laser tape-out process, such as Figure 3 shown.
[0018] In the present embodiment 1, the substrate 1, the lower cladding layer 2, the lower waveguide layer 3 and the current blocking layer 6 are N-type doped structures, and the upper waveguide layer 5, the buried upper waveguide layer 7, the upper cladding layer 8 and the cap layer 9 are P-type doped structures. When the current is injected from the P side to the N side, a PNP structure is formed on the upper and lower sides of the current blocking layer 6, and the current blocking layer 6 blocks the injected current. The current cannot pass through the current blocking layer 6 directly, and can only be concentrated at the junction of the buried upper waveguide layer 7 and the upper waveguide layer 5 to form an effective current injection. Since the current blocking layer 6 is close to the active layer 4, even under a large current injection, a very high current uneven distribution can still be maintained in the active layer 4, thereby forming a gain coupling effect of periodic gain.
[0019] Example 2 Figure 4 and Figure 5 The preparation process of a gain-coupled semiconductor laser based on a current confinement layer in a waveguide according to Embodiment 2 of the present invention is shown.
[0020] like Figure 4 and Figure 5 As shown, the gain-coupled semiconductor laser based on the current limiting layer in the waveguide provided by Embodiment 2 of the present invention includes a substrate 1 and an epitaxial structure grown on the substrate 1, wherein the epitaxial structure includes a lower cladding layer 2, a lower waveguide layer 3, an active layer 4, an upper waveguide layer 5, a current blocking layer 6, a buried upper waveguide layer 7, an upper cladding layer 8, a cap layer 9 and a diffusion blocking layer 11 stacked in sequence from bottom to top, and the upper waveguide layer 5 is etched downward from the diffusion blocking layer 11 to make the current blocking layer 6 a periodic structure, and ion diffusion is performed in the exposed area after etching to form a diffusion region 10.
[0021] The preparation process of the gain-coupled semiconductor laser based on the current confinement layer in the waveguide of Example 2 is as follows: First, a lower cladding layer 2, a lower waveguide layer 3, an active layer 4, an upper waveguide layer 5, a current blocking layer 6, a buried upper waveguide layer 7, an upper cladding layer 8 and a cap layer 9 are sequentially grown on a substrate 1 by MOCVD technology. Figure 4 Then, a periodic current blocking layer 6 is prepared by deposition, photolithography, and etching, and a diffusion region 10 is prepared in the area exposed after etching the diffusion blocking layer 11 by ion diffusion technology, and finally the desired device is obtained by a general semiconductor laser tape-out process, such as Figure 5 As shown, the diffusion barrier layer 11 may be removed in subsequent steps or may be retained.
[0022] In the present embodiment 2, the substrate 1, the lower cladding layer 2, the lower waveguide layer 3 and the current blocking layer 6 are N-type doped structures, and the upper waveguide layer 5, the buried upper waveguide layer 7, the upper cladding layer 8 and the cap layer 9 are P-type doped structures. When the current is injected from the P side to the N side, a PNP structure is formed on the upper and lower sides of the current blocking layer 6, and the current blocking layer 6 blocks the injected current. The current cannot pass through the current blocking layer 6 directly, and can only be concentrated in the diffusion area 10 to form an effective current injection to the upper waveguide layer 5. Since the current blocking layer 6 is close to the active layer 4, even under a large current injection, a very high current uneven distribution can still be maintained in the active layer 4, thereby forming a gain coupling effect of periodic gain.
[0023] It should be noted that the upper waveguide layer 5 can also prevent ions from further diffusing downward.
[0024] In particular, when the substrate 1 is GaAs, InP, GaN, sapphire, or SiC, and the diffused ions are Zn, since Zn is a P-type dopant, the N-type of the current blocking layer 6 can be inverted to the P-type, thereby preparing a periodic current channel in the current blocking layer 6. The periodic current channel can be used to achieve a periodic current difference, and then a periodic carrier difference and a periodic gain difference. By periodically modulating the imaginary part of the refractive index to form a gain coupling mechanism, a gain-coupled DFB is achieved, a mode option is formed, and a single-mode lasing effect is obtained.
[0025] The present invention prepares an N-type doped current blocking layer in a P-type waveguide, so that the active layer obtains periodic current injection. Since the current blocking layer can be prepared in a region very close to the active layer, compared with the surface structure, it is more capable of achieving periodic distribution of carriers in the active layer, thereby obtaining a high gain contrast in the active layer, and being able to maintain single longitudinal mode lasing under high current conditions. The single longitudinal mode lasing operating current and power are higher than those of the surface structure, which can improve the maximum single longitudinal mode lasing power index of the gain-coupled DFB laser and obtain better device performance.
[0026] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.
[0027] The above specific implementations of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.
Claims
1. A gain-coupled semiconductor laser based on a current confinement layer in a waveguide, comprising a substrate and an epitaxial structure grown on the substrate, characterized in that: The epitaxial structure includes a lower cladding layer, a lower waveguide layer, an active layer, an upper waveguide layer, a current blocking layer, a buried upper waveguide layer, an upper cladding layer and a cap layer stacked in sequence from bottom to top. The current blocking layer is a periodic structure and is buried in the buried upper waveguide layer. The substrate, the lower cladding layer, the lower waveguide layer and the current blocking layer are N-type doped structures, and the upper waveguide layer, the buried upper waveguide layer, the upper cladding layer and the cap layer are P-type doped structures.
2. A gain-coupled semiconductor laser based on a current confinement layer in a waveguide, comprising a substrate and an epitaxial structure grown on the substrate, characterized in that: The epitaxial structure includes a lower cladding layer, a lower waveguide layer, an active layer, an upper waveguide layer, a current blocking layer, a buried upper waveguide layer, an upper cladding layer, a cap layer and a diffusion barrier layer stacked in sequence from bottom to top. The upper waveguide layer is etched downward from the diffusion barrier layer to make the current blocking layer a periodic structure. After etching, ion diffusion is carried out in the exposed area to form a diffusion area. The substrate, the lower cladding layer, the lower waveguide layer and the current blocking layer are N-type doped structures, and the upper waveguide layer, the buried upper waveguide layer, the upper cladding layer and the cap layer are P-type doped structures.
3. The gain-coupled semiconductor laser based on the current confinement layer in the waveguide according to claim 2, characterized in that: The diffused ions are zinc ions to prepare periodic current channels in the current blocking layer.