Polarization-controllable high-power vertical cavity surface emitting laser array

Abstract

The invention relates to the technical field of semiconductor lasers, in particular to a polarization-controllable high-power vertical-cavity surface-emitting laser array which comprises a first rhombohedral body, a second rhombohedral body is arranged on the top surface of the first rhombohedral body, positive electrodes are arranged on the two sides of the second rhombohedral body respectively, the positive electrodes are arranged on the first rhombohedral body, and the second rhombohedral body is arranged on the second rhombohedral body. Negative electrodes are symmetrically arranged on the top surface of the second rhombic surface body; the first rhombohedral body comprises a substrate layer, a tunnel layer and a lower layer p-type DBR which are sequentially arranged from bottom to top, and the positive electrode is arranged on the top surface of the lower layer p-type DBR; the second rhombohedron comprises an active region, an oxidation limiting layer and an upper layer n-type DBR which are sequentially arranged from bottom to top; a surface grating structure is arranged between the two negative electrodes; and the surface grating structure and the negative electrodes are arranged on the top surface of the upper-layer n-type DBR. According to the invention, the manufacturing process of the device array is simplified, and the overall performance of the device is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor lasers, and in particular to a polarization-controllable high-power vertical cavity surface emitting laser array. Background Art

[0002] As a new type of semiconductor laser device, Vertical-Cavity Surface-Emitting Laser (VCSEL) has the advantages of low threshold current, low power consumption, fast modulation speed, good beam quality and low cost. It has important applications in optical communications, sensors, 3D sensing (such as face recognition), optical interconnection and lidar. However, due to the limitations of the gallium arsenide material system, conventional lasers cannot control the polarization direction. This unstable polarization state limits the application of lasers in optical components, atomic sensing and spectroscopy.

[0003] In addition, the power of a single laser device is very limited, so it is necessary to arrange multiple units compactly into an array to further increase the output optical power of the laser. Traditional lasers use a pn junction design, in which the p-type region of the structure is located at the top and the n-type region is located at the bottom, that is, a p-up and n-down epitaxial structure on an n-type substrate. Therefore, when arranged in an array, they usually work in a common cathode mode. For the sake of circuit design and packaging process, the polarity is reversed and an np junction design is adopted, that is, an n-up and p-down epitaxial structure on a p-type substrate. The np junction laser array is a common anode laser array driven by an N-MOS (metal oxide semiconductor) field effect transistor, which has a faster response speed and a smaller footprint than a P-MOS field effect transistor. However, due to the high etch pit density (EPD) of the p-type GaAs substrate, the crystal quality of the np junction laser epitaxial structure on the p-type substrate is significantly lower than that of the conventional pn junction laser epitaxial structure on the n-type substrate. The increase in defect density increases the probability of non-radiative recombination, resulting in a decrease in the output optical power of the laser, and the decrease in the output optical power of the laser array is more obvious. Summary of the invention

[0004] The purpose of the present invention is to provide a polarization-controllable high-power vertical cavity surface emitting laser array to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above-mentioned purpose, the present invention provides the following scheme: a polarization-controllable high-power vertical cavity surface emitting laser array, comprising a first rhombus, a second rhombus is arranged on the top surface of the first rhombus, positive electrodes are arranged on both sides of the second rhombus, the positive electrode is arranged on the first rhombus, and negative electrodes are symmetrically arranged on the top surface of the second rhombus; the first rhombus comprises a substrate layer, a tunnel layer, and a lower p-type DBR arranged in sequence from bottom to top, and the positive electrode is arranged on the top surface of the lower p-type DBR; the second rhombus comprises an active area, an oxidation restriction layer, and an upper n-type DBR arranged in sequence from bottom to top; a surface grating structure is arranged between the two negative electrodes, and the surface grating structure and the negative electrode are both arranged on the top surface of the upper n-type DBR.

[0006] Preferably, the cross-sectional area of ​​the first rhombus is greater than the cross-sectional area of ​​the second rhombus.

[0007] Preferably, central axes of the first rhombus and the second rhombus are on the same central axis.

[0008] Preferably, the active region is arranged on the top surface of the lower p-type DBR.

[0009] Preferably, the active region includes a plurality of quantum wells and a plurality of well barriers, and the plurality of quantum wells and the plurality of well barriers are alternately stacked.

[0010] Preferably, the two positive electrodes are arranged on the long axis of the lower p-type DBR.

[0011] Preferably, the two negative electrodes are arranged on the short axis of the upper n-type DBR.

[0012] Preferably, the material of the positive electrode and the negative electrode is Ti or Pt.

[0013] The present invention discloses the following technical effects:

[0014] The present invention utilizes a tunnel layer to perform polarity conversion to avoid the influence of high defect density of the lower p-type DBR; utilizes an oxidized limiting layer to improve the device's regulation of current and light field, while improving the polarization stability of the device; utilizes a surface grating structure formed by etching to adjust the emission wavelength, improve output coupling efficiency and polarization stability, and thus improve the overall performance of the device; the epitaxial structure simplifies the manufacturing process of the device array, improves the output optical power and power conversion efficiency of the device, and realizes the light output of a high-power device array; the present invention not only simplifies the manufacturing process of the device array, but also effectively improves the overall performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 It is a schematic diagram of the cross-sectional structure of the present invention;

[0017] Figure 2 It is a schematic diagram of the top view structure of the present invention;

[0018] Figure 3 It is a schematic diagram of the top view structure of the laser array of the present invention;

[0019] Among them, 100, substrate layer; 200, tunnel layer; 300, lower p-type DBR; 400, positive electrode; 500, active region; 600, oxidation restriction layer; 700, upper n-type DBR; 800, negative electrode; 900, surface grating structure. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Embodiment 1

[0023] Reference Figure 1-Figure 3 The present invention provides a polarization-controllable high-power vertical cavity surface emitting laser array, comprising a first rhombus, a second rhombus is arranged on the top surface of the first rhombus, positive electrodes 400 are arranged on both sides of the second rhombus, the positive electrode 400 is arranged on the first rhombus, and negative electrodes 800 are symmetrically arranged on the top surface of the second rhombus; the first rhombus comprises a substrate layer 100, a tunnel layer 200, and a lower p-type DBR 300 arranged in sequence from bottom to top, and the positive electrode 400 is arranged on the top surface of the lower p-type DBR 300; the second rhombus comprises an active region 500, an oxidation restriction layer 600, and an upper n-type DBR 700 arranged in sequence from bottom to top; a surface grating structure 900 is arranged between the two negative electrodes 800, and the surface grating structure 900 and the negative electrode 800 are both arranged on the top surface of the upper n-type DBR 700.

[0024] A distributed Bragg reflector (DBR) is a reflector used in semiconductor lasers. It uses a Bragg grating to act as a reflector. A section of doped fiber is packaged between two sections of Bragg gratings, and gain is provided by pumping the doped fiber in the middle.

[0025] The P-type DBR is a distributed Bragg reflector made of P-type semiconductor material. It acts as a top reflector in the laser and forms a resonant cavity with the N-type DBR at the bottom. The main function of the P-type DBR is to reflect light of a specific wavelength while allowing light of other wavelengths to pass through. In high-power vertical cavity surface emitting lasers, the design and optimization of the P-type DBR is critical to achieving high efficiency and low series resistance.

[0026] N-type DBR is a distributed Bragg reflector made of N-type semiconductor material. It acts as a bottom reflector in the laser and forms a resonant cavity with the top P-type DBR. The main function of N-type DBR is also to reflect light of a specific wavelength while allowing light of other wavelengths to pass through. In VCSEL, the potential distribution of N-type DBR has a significant effect on the threshold characteristics of the laser, so the potential in both P-type and N-type DBR needs to be considered during design and simulation.

[0027] The present invention utilizes the tunnel layer 200 to perform polarity conversion to avoid the influence of the high defect density of the lower p-type DBR 300; utilizes the oxidation restriction layer 600 to improve the device's regulation of current and light field, while improving the polarization stability of the device; utilizes the surface grating structure 900 formed by etching to adjust the emission wavelength, improve the output coupling efficiency and polarization stability, and thus improve the overall performance of the device; the epitaxial structure simplifies the manufacturing process of the device array, improves the output optical power and power conversion efficiency of the device, and realizes the light output of a high-power device array; the present invention not only simplifies the manufacturing process of the device array, but also effectively improves the overall performance of the device.

[0028] In a further optimized solution, the cross-sectional area of ​​the first rhombus is larger than the cross-sectional area of ​​the second rhombus, so as to facilitate the arrangement of the positive electrode 400 .

[0029] In a further optimized solution, the central axes of the first rhombus and the second rhombus are on the same central axis. The first rhombus and the second rhombus are coaxially arranged, which effectively improves the polarization stability of the device.

[0030] In a further optimized solution, the active region 500 is disposed on the top surface of the lower p-type DBR 300 .

[0031] According to a further optimized solution, the active region 500 includes a plurality of quantum wells and a plurality of well barriers, and the plurality of quantum wells and the plurality of well barriers are alternately stacked.

[0032] By changing the injection distribution of carriers in the active region 500, the device light field distribution is optimized, the light field is more concentrated near the active region, the interaction between light and matter is improved, the gain of the device is enhanced, the device threshold current is reduced, and the device output light power and electro-optical conversion efficiency are improved.

[0033] In a further optimized solution, two positive electrodes 400 are arranged on the long axis of the lower p-type DBR 300 .

[0034] In a further optimized solution, two negative electrodes 800 are disposed on the short axis of the upper n-type DBR 700 .

[0035] According to a further optimization scheme, the material of the positive electrode 400 and the negative electrode 800 is Ti or Pt.

[0036] The positive electrode 400 and the negative electrode 800 form an intra-cavity asymmetric electrode, and the heat dissipation capacity and carrier recombination efficiency of the device are improved by the intra-cavity asymmetric electrode.

[0037] Intra-cavity asymmetric electrodes are special electrode designs that are usually used in optoelectronic devices such as photodetectors. The characteristic of this design is that metal electrodes with different work functions are deposited on the surface of the semiconductor layer to form an asymmetric structure. For example, an asymmetric electrode of a photodetector may include a first metal electrode with a work function greater than 5.0 eV and a second metal electrode with a work function between 4.2-4.4 eV.

[0038] The design of asymmetric electrodes can improve the performance of optoelectronic devices. For example, in a photodetector, due to the different material work functions of the first electrode and the second electrode, a Schottky barrier height can be generated between each electrode and the semiconductor layer. When the first electrode and the second electrode are made of different materials, a Schottky barrier height difference will be generated between the first electrode and the second electrode on the semiconductor layer. This Schottky barrier height difference can effectively separate the photogenerated electron-hole pairs under the action of the built-in electric field, thereby improving the photoresponsivity of the device.

[0039] The method for preparing the asymmetric electrode generally includes depositing the material of the first metal electrode and the material of the second metal electrode on the surface of the semiconductor layer. The deposition method includes electron beam evaporation, magnetron sputtering, etc. Before deposition, it may also include forming the shape of the metal electrode on the surface of the semiconductor layer, and ultrasonically cleaning the semiconductor layer.

[0040] The present invention adopts the n-up epitaxial structure and the p-down epitaxial structure of the substrate layer 100, and uses the tunnel layer 200 as a conversion layer to connect the lower p-type DBR 300 and the substrate layer 100; at the same time, a diamond-shaped oxidation restriction layer 600 and a diamond-shaped mesa structure are adopted; while optimizing current injection, a full semiconductor intra-cavity electrode structure is adopted, and a surface grating structure 900 is introduced at the light output of the upper n-type DBR 700.

[0041] The n-up epitaxial structure refers to a structure in which an n-type semiconductor layer is grown on an n-type substrate. The n-type semiconductor layer serves as the positive electrode or anode of the device, while the n-type substrate serves as the negative electrode or cathode.

[0042] The p-down epitaxial structure refers to a structure in which a p-type semiconductor layer is grown on an n-type substrate. The p-type semiconductor layer serves as the negative electrode or cathode of the device, while the n-type substrate serves as the positive electrode or anode.

[0043] The present invention effectively avoids the influence of high defect density of p-type GaAs substrate by adopting np junction laser of substrate layer 100, improves output optical power and power conversion efficiency compared with conventional pn junction laser, and simplifies the circuit design problem of laser array; tunnel junction in conventional laser is generally used to control current diffusion and absorption loss of light field in device or to reverse polarity of upper DBR, while tunnel layer 200 of the present invention is placed between lower p-type DBR 300 and substrate layer 100 for polarity conversion, so that array avoids the influence of high defect density of p-type substrate itself while adopting common anode laser array; rhombus oxidation limit The manufacturing layer 600 effectively realizes the precise control of the current and the light field, improves the polarization suppression ratio of the device, stabilizes the polarization direction of the device, and can be well applied in the scenarios with frequency stability requirements such as atomic sensing and gas detection; at the same time, the present invention improves the heat dissipation capacity, carrier recombination efficiency and mode stability of the device by combining the design of the diamond multi-table intra-cavity asymmetric electrode; due to the obvious difference in the reflectivity of the two polarization modes in the device due to the surface grating structure, the mirror loss of the two polarization modes is different, thereby realizing the control of the device over polarization and making the device have a single polarization mode.

[0044] P-type GaAs (P-type Gallium Arsenide) is a semiconductor material, where "P-type" refers to the doping type of the semiconductor. In semiconductors, doping refers to the process of adding trace amounts of impurity elements to semiconductor materials to change their electronic structure and conductivity. P-type semiconductors are achieved by adding elements belonging to Group III elements (such as boron, aluminum, gallium, indium, etc.). These elements have only three valence electrons, so a vacancy, or "hole", is formed in the structure. These "holes" can act as carriers of charge, making the semiconductor become P-type.

[0045] Embodiment 2

[0046] This embodiment provides a novel method for manufacturing a vertical cavity surface emitting laser array, which specifically includes:

[0047] The tunnel layer 200, the lower p-type DBR 300, and the upper n-type upper DBR 700 are grown on the substrate layer 100 from bottom to top by using the metal organic chemical vapor deposition (MOVCD) technology; the epitaxial structure on the substrate layer 100 enhances the carrier mobility, reduces the series resistance, and improves the output optical power and the power conversion efficiency; by placing the tunnel layer 200 between the substrate layer 100 and the lower p-type DBR 300 for junction polarity inversion, the influence of the high defect density of the p-type GaAs substrate is effectively avoided, the current injection efficiency is improved, and the output optical power and the power conversion efficiency of the laser are improved.

[0048] After epitaxial growth, inductively coupled plasma (ICP) etching technology is used to form diamond-shaped terraces, and a diamond-shaped oxide restriction layer 600 is formed by wet oxidation technology; the diamond-shaped oxide restriction layer 600 is surrounded by an upper n-type DBR 700; the diamond-shaped oxide restriction layer 600 can more effectively regulate current and light field, and by adjusting the appropriate diamond-shaped oxide aperture, it can not only control the polarization state of the device, improve the polarization suppression ratio, and enable the device to achieve a single polarization mode; it can also effectively reduce the polarization instability caused by temperature and current changes.

[0049] At the same time, the design of the diamond-shaped multi-table intra-cavity asymmetric electrode improves the carrier injection efficiency, thereby improving the laser emission efficiency; reduces the accumulation of device heat in the active area, thereby improving the device's heat dissipation capacity, and is conducive to achieving high-frequency modulation and polarization control; the upper n-type DBR700 is etched using ICP etching technology to form a surface grating structure 900, thereby adjusting the device's emission wavelength, improving the beam quality, and improving the device's light output coupling efficiency and polarization stability.

[0050] Compared with conventional laser arrays, the laser array of the present invention has higher output optical power, power conversion efficiency, heat dissipation capacity and polarization stability. The enhanced performance of the laser array effectively improves the application in fields such as high-power 3D sensing and laser radar.

[0051] The present invention utilizes a substrate layer 100, a tunnel layer 200, a lower p-type DBR 300, an active region 500, an oxidized limiting layer 600, an upper n-type DBR 700, an intra-cavity asymmetric electrode, and a surface grating structure 900 etched and grown on the upper n-type DBR 700 to more effectively limit and select the device laser mode, suppress the excitation of high-order modes, achieve single-mode output of the device, improve the stability and reliability of the output light, and obtain better beam quality and coherence; fix the polarization direction of the device laser, reduce the change and fluctuation of the polarization state, and improve the polarization stability and polarization stability of the laser. The laser output by the laser has a purer polarization state by improving the vibration suppression ratio; by changing the injection distribution of carriers in the active area 500, the device light field distribution is optimized, the light field is more concentrated near the active area 500, the interaction between light and matter is improved, the gain of the device is enhanced, the threshold current of the device is reduced, the output optical power of the device and the electro-optical conversion efficiency are improved; the heat dissipation capacity of the device is enhanced, the stress concentration and material performance degradation caused by uneven temperature are reduced, the operating temperature of the device is reduced, the stability and reliability of the device are improved, the service life of the device is extended, and the occurrence of local overheating is avoided.

[0052] The present invention improves the purity of the spectrum and can obtain a narrower spectral line width; simplifies the structure of the device, makes the laser more compact and miniaturized, and can achieve large-scale integration; improves the modulation performance of the device, increases the response speed of the device to the modulation signal and its modulation bandwidth; the manufacturing process is compatible with the existing process, can achieve large-scale parallel production, and improves the production efficiency of the device; in summary, the structure optimizes the performance of the overall laser and its laser array.

[0053] The working principle of N-MOS is based on the electric field effect, which controls the current between the source and the drain by applying different voltages between the gate and the source. When the gate voltage is high, the transistor is turned on, allowing current to flow from the drain to the source (electrons flow from the source to the drain); when the gate voltage is low, the transistor is turned off and current cannot pass.

[0054] N-MOS has the following properties:

[0055] Small on-resistance: Due to the high electron mobility, the on-resistance of n-MOSFET is relatively small.

[0056] Fast: The high electron mobility and the typically short distance between the source and drain make the n-MOSFET switch quickly.

[0057] Low power consumption: In the on state, n-MOSFET consumes relatively less power.

[0058] Poor high temperature resistance: At high temperatures, the performance of n-MOSFET decreases rapidly because increased thermal excitation leads to the appearance of more minority carriers.

[0059] P-MOS, the full name of which is P-Channel Metal-Oxide-Semiconductor Field-Effect Transistor (PMOS), is a type of transistor commonly used in semiconductor technology. Its basic structure includes a P-type substrate, a P-type doped source and drain, and a control gate.

[0060] The working principle of P-MOS transistor is based on the control of channel conductivity by gate voltage. When negative voltage is applied to the gate, the P-type channel is attracted to form a conduction channel, allowing current to flow from the drain to the source; when the gate voltage is higher than the source voltage, the P-type channel is broken down and cannot form a conduction channel, and the PMOS tube is in the cut-off state.

[0061] The laser array of the present invention adopts a common anode laser array driven by an N-MOS field effect transistor, which has a simpler manufacturing method, a faster response speed and a smaller footprint than a traditional P-MOS field effect transistor. The laser array has higher output light power and power conversion efficiency.

[0062] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0063] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A polarization-controllable high-power vertical cavity surface emitting laser array, characterized in that: It comprises a first rhombus, a second rhombus is arranged on the top surface of the first rhombus, positive electrodes (400) are arranged on both sides of the second rhombus, the positive electrode (400) is arranged on the first rhombus, and negative electrodes (800) are symmetrically arranged on the top surface of the second rhombus; The first rhombohedron comprises a substrate layer (100), a tunnel layer (200), and a lower p-type DBR (300) which are arranged in sequence from bottom to top, and the positive electrode (400) is arranged on the top surface of the lower p-type DBR (300); The second rhombohedron comprises an active region (500), an oxidation restriction layer (600), and an upper n-type DBR (700) which are arranged in sequence from bottom to top; A surface grating structure (900) is arranged between the two negative electrodes (800), and the surface grating structure (900) and the negative electrode (800) are both arranged on the top surface of the upper n-type DBR (700).

2. The polarization-controllable high-power vertical cavity surface emitting laser array according to claim 1, characterized in that: The cross-sectional area of ​​the first rhombus is greater than the cross-sectional area of ​​the second rhombus.

3. The polarization-controllable high-power vertical cavity surface emitting laser array according to claim 1, characterized in that: Central axes of the first rhombus and the second rhombus are located on the same central axis.

4. The polarization-controllable high-power vertical cavity surface emitting laser array according to claim 1, characterized in that: The active region (500) is disposed on the top surface of the lower p-type DBR (300).

5. The polarization-controllable high-power vertical cavity surface emitting laser array according to claim 1, characterized in that: The active region (500) comprises a plurality of quantum wells and a plurality of well barriers, wherein the plurality of quantum wells and the plurality of well barriers are alternately stacked.

6. The polarization-controllable high-power vertical cavity surface emitting laser array according to claim 1, characterized in that: The two positive electrodes (400) are arranged on the long axis of the lower p-type DBR (300).

7. The polarization-controllable high-power vertical cavity surface emitting laser array according to claim 1, characterized in that: The two negative electrodes (800) are arranged on the short axis of the upper n-type DBR (700).

8. The polarization-controllable high-power vertical cavity surface emitting laser array according to claim 1, characterized in that: The material of the positive electrode (400) and the negative electrode (800) is Ti or Pt.

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