Single-mode high-power vertical cavity surface emitting laser structure and manufacturing method thereof

Abstract

The invention discloses a single-mode high-power vertical-cavity surface-emitting laser structure and a manufacturing method thereof. The laser comprises a substrate layer, a lower-layer N-type DBR, an active region, an asymmetric oxidation limiting layer, a space layer, an upper-layer P-type DBR and a surface relief structure which are sequentially arranged from bottom to top. The substrate layer and the lower-layer N-type DBR form a first ellipse cylinder; the active region, the asymmetric oxidation limiting layer and the space layer form a second ellipse cylinder; the upper-layer P-type DBR and the surface embossment structure form a third ellipse cylinder; the negative electrodes are arranged at the two ends of the long axis of the first ellipsoid cylinder. The positive electrodes are arranged at the two ends of the short axis of the second ellipsoid cylinder; and the negative electrode and the positive electrode form an intra-cavity asymmetric electrode structure. According to the invention, the current injection efficiency, the optical coupling efficiency, the single-mode stability and the controllability on the output wavelength of the device are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor lasers, and in particular relates to a single-mode high-power vertical cavity surface emitting laser structure and a manufacturing method thereof. Background Art

[0002] As an emerging semiconductor laser technology, Vertical-Cavity Surface-Emitting Laser (VCSEL) has demonstrated its significant advantages in many fields. VCSEL has been widely used in optical communications, sensors, 3D sensing technologies such as face recognition, optical interconnection, and lidar due to its compact structure, low power consumption, fast modulation speed, and high cost-effectiveness. Compared with traditional edge-emitting lasers, VCSEL is unique in that it can emit light beams in a direction perpendicular to the substrate, which makes it easier to couple with optical fibers and suitable for arrayed applications, thus playing a key role in integrated optical systems.

[0003] Despite the above advantages of VCSEL technology, there are still some technical challenges in existing designs. In particular, in terms of mode control, polarization stability and beam quality, traditional VCSEL designs face some limitations. In the current injection area, the inhomogeneity of the current and light field distribution around the active layer is the main reason for the reduction of laser efficiency, mode instability and increased laser beam divergence. In order to solve these problems, the oxidation confinement layer technology is widely used. By oxidizing high-aluminum materials such as AlGaAs to form a lateral confinement structure, the distribution of current and light field can be effectively controlled, thereby improving the efficiency of VCSEL.

[0004] However, existing oxide confinement layers usually adopt symmetrical circular or elliptical structures. In specific application scenarios, these symmetrical structures still cannot fully meet the needs of performance optimization, especially when increasing the modulation bandwidth and reducing the oxide aperture to increase the VCSEL rate, there will be challenges in optical loss and thermal management issues. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a single-mode high-power vertical cavity surface emitting laser structure and a manufacturing method thereof to solve the above problems existing in the prior art.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a single-mode high-power vertical cavity surface emitting laser structure, comprising:

[0007] From bottom to top, there are a substrate layer, a lower N-type DBR, an active area, an asymmetric oxidation restriction layer, a space layer, an upper P-type DBR, and a surface relief structure.

[0008] The substrate layer and the lower N-type DBR constitute a first partial elliptical cylinder; the active area, the asymmetric oxidation restriction layer, and the space layer constitute a second partial elliptical cylinder; the upper P-type DBR and the surface relief structure constitute a third partial elliptical cylinder;

[0009] The negative electrodes are arranged at both ends of the long axis of the first ecliptic cylinder; the positive electrodes are arranged at both ends of the short axis of the second ecliptic cylinder; the negative electrode and the positive electrode constitute an intra-cavity asymmetric electrode structure.

[0010] Preferably, the first partial elliptical cylinder, the second partial elliptical cylinder and the third partial elliptical cylinder are all composed of two ellipses with the same short axis and different long axes, and are designed as coaxial elliptical cylinders.

[0011] Preferably, the asymmetric oxidation restriction layer is composed of two ellipses with the same short axis and different long axes.

[0012] Preferably, the space layer is doped by modulation to optimize parasitic resistance.

[0013] Preferably, the active region includes a plurality of active regions, each of which is formed by alternately stacking a plurality of pairs of quantum wells and well barriers.

[0014] Preferably, the surface relief structure is formed by deposition and etching on top of the laser structure.

[0015] Preferably, the intra-cavity asymmetric electrode adopts asymmetric current injection.

[0016] Preferably, the material of the intra-cavity asymmetric electrode is Ti or Pt.

[0017] In a second aspect, the present invention further provides a method for manufacturing a single-mode high-power vertical cavity surface emitting laser structure, comprising the following steps:

[0018] By using molecular beam epitaxy or metal organic chemical vapor deposition method, a lower layer of N-type DBR is epitaxially grown from bottom to top on the substrate layer to form a first partial elliptical cylinder;

[0019] Epitaxially growing an active region and an oxidized confinement layer on the first elliptical cylinder to form an asymmetric oxidized confinement layer, and epitaxially growing a space layer to form a second eccentric elliptical cylinder;

[0020] Continue epitaxially growing the third partial elliptical cylinder, including the upper P-type DBR;

[0021] Negative electrodes are deposited at both long-axis ends of the first partial elliptical cylinder, and positive electrodes are deposited at both short-axis ends of the second partial elliptical cylinder to form an intra-cavity asymmetric electrode;

[0022] A relief structure is deposited and etched on the top of the laser structure.

[0023] Compared with the prior art, the present invention has the following advantages and technical effects:

[0024] The present invention provides a single-mode high-power vertical cavity surface-emitting laser structure, including: a substrate layer, a lower N-type DBR, an active region, an asymmetric oxidation confinement layer, a space layer, an upper P-type DBR, and a surface relief structure are sequentially arranged from bottom to top; wherein, the substrate layer and the lower N-type DBR form a first partial elliptical cylinder; the active region, the asymmetric oxidation confinement layer, and the space layer form a second partial elliptical cylinder; the upper P-type DBR and the surface relief structure form a third partial elliptical cylinder; negative electrodes are arranged at both ends of the long axis of the first partial elliptical cylinder; positive electrodes are arranged at both ends of the short axis of the second partial elliptical cylinder; the negative electrodes and the positive electrodes form an intra-cavity asymmetric electrode structure.

[0025] The present invention adopts an asymmetric oxidation confinement layer with a partial elliptical mesa design, and a space layer is arranged near the active region. While optimizing current injection, a fully semiconductor intra-cavity asymmetric electrode structure can be adopted, and a relief structure is introduced at the light output of the upper DBR. Through the asymmetric partial elliptical oxidation confinement layer, effective precise control of current injection and light field is achieved, the excitation of high-order modes is suppressed, the mode coupling effect is strengthened, and the modulation characteristics, single-mode stability, and output efficiency of the device are significantly improved; in addition, this design optimizes the heat dissipation performance of the device, which helps to improve the operating stability at high power. By setting the space layer, the cavity length can be precisely regulated to achieve stable control of the emission wavelength and improve the heat dissipation and thermal management performance of the device. By combining the design of an elliptical multi-mesa intra-cavity electrode, asymmetric current injection is adopted to improve the heat dissipation ability, carrier recombination efficiency, and mode stability of the device.

[0026] The present invention improves the single-mode output power through the relief structure, significantly reduces the reflection loss by improving the beam coupling efficiency, improves the light output power and overall coupling efficiency, and particularly exhibits excellent performance in fiber coupling applications. Through the overall structure composed of a partial elliptical mesa, a relief structure, and an intra-cavity asymmetric electrode, single-mode high power of the device is achieved. Description of the Drawings

[0027] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0028] Figure 1 is a cross-sectional view of a device structure according to an embodiment of the present invention;

[0029] Figure 2 A top view of a device structure according to an embodiment of the present invention;

[0030] Among them, 100, substrate layer; 200, lower N-type DBR; 300, negative electrode; 400, active area; 500, asymmetric oxidation restriction layer; 600, space layer; 700, positive electrode; 800, upper P-type DBR; 900, surface relief structure. DETAILED DESCRIPTION

[0031] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0032] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0033] like Figure 1 As shown, this embodiment provides a single-mode high-power vertical cavity surface emitting laser structure, including:

[0034] From bottom to top, the first partial elliptical table GaAs substrate 100, the lower N-type DBR 200, the negative electrode 300 distributed on the first elliptical table, the second partial elliptical table containing the active area 400, the asymmetric oxidation restriction layer 500, the space layer 600, the positive electrode 700 distributed on the second partial elliptical table, and the third partial elliptical table containing the upper P-type DBR 800 and the surface relief structure 900 formed by etching. The space layer 600 is at the top of the active area 400. The intra-cavity asymmetric electrode is composed of the negative electrode 300 distributed on the first partial elliptical table and the positive electrode 700 distributed on the second partial elliptical table. The negative electrode for injecting electrons is placed at both ends of the long axis of the elliptical table of the lower N-type DBR 200, and the positive electrode for injecting holes is placed at both ends of the short axis in the space layer of the second partial elliptical table. This structure improves the single-mode stability, output efficiency and overall coupling efficiency of the device, optimizes the heat dissipation performance of the device, and realizes stable control of the emission wavelength.

[0035] Figure 2As an innovative implementation scheme, the overall structure of the device is a partial elliptical multi-table structure, the substrate 100 and the lower N-type DBR 200 form a first partial elliptical cylinder, the first partial elliptical table is composed of a short axis R 1 , the major axis is R 2 , and the minor axis is R 1 , the major axis is R 3 It is made up of semi-elliptical tabletops.

[0036] The active area 400, the oxidation restriction layer 500, and the space layer 600 together constitute a second elliptical cylinder. The second elliptical cylinder is also composed of semi-elliptical table surfaces with the same short axis and different long axes. The third elliptical table surface is composed of an upper P-type DBR 800 and a surface relief structure 900. The first elliptical cylinder, the second elliptical cylinder, and the third elliptical cylinder are designed as coaxial elliptical cylinders, and this structure optimizes the heat dissipation capacity of the device. The shaded portion on the first elliptical table surface is the negative electrode 300, and the shaded portion on the second elliptical table surface is the positive electrode 700.

[0037] As an innovative implementation scheme, the surface relief structure 900 is used to improve the optical coupling efficiency of the device, and the non-elliptical multi-table and intra-cavity asymmetric electrodes use asymmetric current injection to improve the device's heat dissipation capacity, carrier recombination efficiency and mode stability.

[0038] Specifically, the active region includes a plurality of active regions, which is greater than or equal to 2, but not limited to 3, 4, 5, etc., and each active region is formed by alternatingly stacking a plurality of pairs of quantum wells and well barriers.

[0039] As an additional implementation method, the laser structure includes specific lithography and wet oxidation technology after epitaxial growth to form an asymmetric oxidation-restricted elliptical table. The elliptical table is composed of two ellipses with the same short axis and different long axes. Compared with the symmetrical elliptical oxidation restriction layer, the elliptical oxidation restriction layer can more effectively realize current injection and precise control of the light field. At the same time, by adjusting to a suitable elliptical oxidation aperture, it can have a greater impact on the single-mode stability and output efficiency of the device. At the same time, this design can also make up for the lack of heat dissipation performance of the symmetrical oxidation restriction layer elliptical table, which helps to improve the operation stability under high power.

[0040] As an additional implementation method, by setting a space layer on the oxide layer and modulating the doped space layer, the parasitic resistance is optimized and the parasitic cutoff frequency is increased. By combining the design of the intra-cavity electrode with a partial elliptical multi-table, asymmetric current injection is adopted to reduce the phenomenon of carrier congestion, so that the injected holes and electrons are effectively recombined, and the current distribution is uniform, so that more current is injected into the active area, thereby improving the luminous efficiency and light output power of the device, and also improving the heat dissipation capacity and polarization stability of the device, which is beneficial to the polarization of the emitted light perpendicular to the current direction. The heat dissipation capacity, carrier recombination efficiency and mode stability of the device are improved. Depositing and etching on the upper DBR to form a relief structure can increase the single-mode output light power, improve the coupling efficiency of the light beam, and improve the overall coupling efficiency.

[0041] In summary, this embodiment proposes to form an asymmetric oxidation-limited elliptical table by etching and oxidation after epitaxial growth, and then continue to epitaxially grow a space layer, combine an intra-cavity electrode with a partial elliptical multi-table, and epitaxially grow an upper DBR, and deposit and etch relief for a laser structure of a VCSEL structure. The purpose is to use the asymmetric oxidation-limited partial elliptical table to improve the effective current injection efficiency of the device and further control the light field, while improving the single-mode stability of the device, and use the thickness and refractive index of the space layer to achieve effective control of the cavity length, thereby further effectively controlling the output wavelength of the device. By combining the design of the intra-cavity electrode with a partial elliptical multi-table and adopting asymmetric current injection, the heat dissipation capacity, carrier recombination efficiency and mode stability of the device are improved; and the relief structure formed by etching is used to improve the optical coupling efficiency of the device, thereby improving the overall performance of the device.

[0042] Beneficial effects of this embodiment:

[0043] The present embodiment discloses a single-mode high-power vertical cavity surface emitting laser structure, the purpose of which is to utilize an asymmetric oxidation confinement layer, an epitaxially formed space layer, an elliptical multi-table intra-cavity asymmetric electrode, and a relief structure etched and grown on a P-type upper DBR to improve the device's current injection efficiency, optical coupling efficiency, single-mode stability, and controllability of the device's output wavelength, improve the device's temperature performance and thermal management at high power, and thereby optimize the overall laser performance.

[0044] Embodiment 2

[0045] This embodiment provides a method for manufacturing a single-mode high-power vertical cavity surface emitting laser structure, which specifically includes:

[0046] S1. On the GaAs substrate 100, a lower N-type DBR 200 is epitaxially grown from bottom to top by molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOCVD) technology, and then etched to form a first elliptical table.

[0047] The specific method is to use dry etching to design the direction with faster etching rate as the short axis of the ellipse and the direction with slower etching rate as the long axis of the ellipse according to the anisotropy of the material etching rate and the values ​​of the etching rates in each direction, so that the etching aperture can obtain a better circular pattern.

[0048] S2, epitaxially growing the active region 400 and the AlGaAs oxidation restriction layer 500 on the first elliptical table, and performing oxidation and oxidation, thus forming a partially elliptical oxidation hole. Next, epitaxially growing the space layer 600, and forming the basis of the second partially elliptical table.

[0049] The second partial elliptical table is composed of two ellipses with the same short axis and different long axes, which enables more precise control of the current and light field in this area. This splicing design can not only further optimize the current distribution and ensure that the current is concentrated in the active area, but also improve the mode control of the laser and avoid the occurrence of unstable or asymmetric distribution of the laser mode.

[0050] S3, continue to epitaxially grow the third layer of elliptical table structure, the upper P-type DBR800 and deposit negative electrodes 300 on the two long axis ends of the first elliptical table and positive electrodes 700 on the two short axis ends of the second elliptical table, the electrode material is Ti or Pt, thereby forming an intra-cavity asymmetric electrode.

[0051] Combined with the partial elliptical multi-table structure, and because the mobility of holes is less than that of electrons, the above electrode structure can stabilize polarization and effectively recombine the injected holes and electrons, reduce carrier congestion, and make the current distribution uniform, so that more current is injected into the active area, thereby improving the luminous efficiency, light output power and mode stability of the device. At the same time, through the alternating arrangement of high and low refractive index materials, the upper P-type DBR800 and the lower N-type DBR200 jointly achieve the effect of high reflectivity, improve the light feedback efficiency and reduce the loss in the cavity.

[0052] S4. Depositing and etching a relief structure 900 on the top of the device.

[0053] The introduction of the relief structure increases the single-mode output power, while improving the light beam coupling efficiency and increasing the overall optical output power of the device.

[0054] In general, the VCSEL structure of this embodiment effectively optimizes current injection, heat dissipation and mode stability through the two mesa designs and the application of asymmetric oxide confinement layers, as well as asymmetric electrodes in the intra-cavity, and improves the single-mode output power. This structure overcomes the thermal effect problem of traditional VCSELs in high-power applications, while significantly improving the light output quality and reliability of the device.

[0055] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A single-mode high-power vertical cavity surface emitting laser structure, characterized in that: include: From bottom to top, there are a substrate layer, a lower N-type DBR, an active area, an asymmetric oxidation restriction layer, a space layer, an upper P-type DBR, and a surface relief structure. The substrate layer and the lower N-type DBR constitute a first partial elliptical cylinder; the active area, the asymmetric oxidation restriction layer, and the space layer constitute a second partial elliptical cylinder; the upper P-type DBR and the surface relief structure constitute a third partial elliptical cylinder; The negative electrodes are arranged at both ends of the long axis of the first ecliptic cylinder; the positive electrodes are arranged at both ends of the short axis of the second ecliptic cylinder; the negative electrode and the positive electrode constitute an intra-cavity asymmetric electrode structure.

2. The laser structure according to claim 1, characterized in that: The first partial elliptical cylinder, the second partial elliptical cylinder, and the third partial elliptical cylinder are all composed of two ellipses with the same short axis and different long axes, and are designed as coaxial elliptical cylinders.

3. The laser structure according to claim 1, characterized in that: The asymmetric oxidation restriction layer is composed of two ellipses with the same short axis and different long axes.

4. The laser structure according to claim 1, characterized in that: The space layer is doped by modulation to optimize the parasitic resistance.

5. The laser structure according to claim 1, characterized in that: The active region includes a plurality of active regions, and each active region is formed by alternately stacking a plurality of pairs of quantum wells and well barriers.

6. The laser structure according to claim 1, characterized in that: The surface relief structure is formed by deposition and etching on top of the laser structure.

7. The laser structure according to claim 1, characterized in that: The intra-cavity asymmetric electrode adopts asymmetric current injection.

8. The laser structure according to claim 1, characterized in that: The material of the intra-cavity asymmetric electrode is Ti or Pt.

9. A method for manufacturing a single-mode high-power vertical cavity surface emitting laser structure according to any one of claims 1 to 8, characterized in that: The following steps are involved: By using molecular beam epitaxy or metal organic chemical vapor deposition method, a lower N-type DBR is epitaxially grown from bottom to top on the substrate layer to form a first partial elliptical cylinder; Epitaxially growing an active region and an oxidized confinement layer on the first elliptical cylinder to form an asymmetric oxidized confinement layer, and epitaxially growing a space layer to form a second eccentric elliptical cylinder; Continue epitaxially growing the third partial elliptical cylinder, including the upper P-type DBR; Negative electrodes are deposited on two long axis ends of the first elliptical cylinder, and positive electrodes are deposited on two short axis ends of the second elliptical cylinder to form an intra-cavity asymmetric electrode; A relief structure is deposited and etched on top of the laser structure.

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