Coherent coupling multi-junction cascade vertical cavity surface emitting laser array and preparation method thereof

Abstract

The invention provides a coherent coupling multi-junction cascade vertical cavity surface emitting laser array and a preparation method thereof. The coherent coupling multi-junction cascade vertical cavity surface emitting laser array comprises a heat sink substrate, an N-type electrode, an N-type reflector, a multi-layer active region, a reverse bias tunnel junction, a refractive index guide layer, a P-type reflector and a P-type electrode which are sequentially stacked in a first direction, the reverse bias tunnel junctions are located between the adjacent active regions; the array comprises a plurality of light-emitting units distributed in the second direction, interval areas are arranged between the adjacent light-emitting units, and the second direction is perpendicular to the first direction; the refractive index guide layer and the P-type electrode are located in the spacer region. Light beams generated by the light-emitting units can be propagated from the light-emitting units with the low effective refractive index to the interval areas with the high effective refractive index, namely, light beam leakage, coherent coupling, phase locking and improvement of light beam quality and spectral quality are achieved, and the multi-junction VCSEL array with high power density, low divergence angle and high spectral quality can be obtained.

Description

Technical Field

[0001] The present application relates to the field of lasers, and particularly to a coherently coupled multi-junction cascaded vertical cavity surface emitting laser array and a method for preparing the same. Background Art

[0002] Multi-junction cascaded vertical cavity surface emitting laser (VCSEL) arrays have been widely used in fields such as lidar, three-dimensional sensing, and infrared illumination. However, the beam quality and spectral quality of existing VCSEL arrays are poor and cannot meet the usage requirements. For example, they will have an adverse impact on the detection distance and signal-to-noise ratio of the detection system. Summary of the Invention

[0003] In view of this, the purpose of the present application is to provide a coherently coupled multi-junction cascaded vertical cavity surface emitting laser array and a method for preparing the same, which can improve the beam quality and spectral quality, and can obtain a multi-junction VCSEL array with high power density, low divergence angle, and high spectral quality. The specific solutions are as follows:

[0004] On the one hand, the present application provides a coherently coupled multi-junction cascaded vertical cavity surface emitting laser array, including:

[0005] A heat sink substrate, an N-type electrode, an N-type mirror, a multi-layer active region, a reverse-biased tunnel junction, a refractive index guiding layer, a P-type mirror, and a P-type electrode stacked in sequence along a first direction; the reverse-biased tunnel junction is located between adjacent active regions;

[0006] The coherently coupled multi-junction cascaded vertical cavity surface emitting laser array includes a plurality of light emitting units distributed in a second direction, and there is a spacing region between adjacent light emitting units, and the second direction is perpendicular to the first direction;

[0007] The refractive index guiding layer and the P-type electrode are located in the spacing region.

[0008] Optionally, the refractive index of the refractive index guiding layer is greater than the refractive indices of the materials of the N-type mirror and the P-type mirror.

[0009] Optionally, when the refractive index of the active region material is greater than the refractive indices of the materials of the N-type mirror and the P-type mirror, the refractive index of the refractive index guiding layer is greater than or equal to the refractive index of the active region quantum well material.

[0010] Optionally, the coherently coupled multi-junction cascaded vertical cavity surface emitting laser array further includes an ion implantation region located in the spacing region;

[0011] The ion implantation region includes the multi-layer active region, and the resistance value of the ion implantation region is higher than a preset resistance value.

[0012] Optionally, the heat sink substrate is a diamond heat sink substrate.

[0013] Optionally, the material system of the coherent coupled multi-junction cascaded vertical cavity surface emitting laser array is InP-based, GaAs-based or GaN-based.

[0014] Optionally, the size of the spacer region in the second direction is determined based on the coupling mode.

[0015] In another aspect, the present application also provides a method for manufacturing a coherent coupled multi-junction cascaded vertical cavity surface emitting laser array, the method comprising:

[0016] Epitaxially forming an N-type mirror, a multi-layer active region and a reverse-biased tunnel junction on an epitaxial substrate in sequence; the reverse-biased tunnel junction is located between adjacent active regions;

[0017] Forming a refractive index guiding layer on a side of the multi-layer active region away from the N-type mirror;

[0018] Removing the refractive index guiding layer in the region where the light emitting unit is located, and retaining the refractive index guiding layer in the spacer region;

[0019] Forming a P-type mirror on a side of the refractive index guiding layer away from the multi-layer active region;

[0020] Forming a P-type electrode in the spacer region;

[0021] Removing the epitaxial substrate, and forming an N-type electrode on a side of the N-type mirror away from the multi-layer active region;

[0022] Forming a heat sink substrate on a side of the N-type electrode away from the N-type mirror to obtain the coherent coupled multi-junction cascaded vertical cavity surface emitting laser array.

[0023] Optionally, before removing the epitaxial substrate, the method further comprises:

[0024] Performing multiple ion implantations on the multi-layer active region to form an ion implantation region; the implantation energy for each ion implantation is in the range of 200 keV - 380 keV, and the resistance value of the ion implantation region is higher than a preset resistance value.

[0025] Optionally, the heat sink substrate is a diamond heat sink substrate, and forming a substrate on a side of the N-type electrode away from the N-type mirror to obtain the coherent coupled multi-junction cascaded vertical cavity surface emitting laser array, comprising:

[0026] Bond the N-type electrode to the diamond heat sink substrate through a bonding technique to obtain the coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array.

[0027] An embodiment of the present application provides a coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array and a preparation method thereof. The coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array includes a heat sink substrate, an N-type electrode, an N-type mirror, a multi-layer active region, a reverse-biased tunnel junction, a refractive index guiding layer, a P-type mirror, and a P-type electrode stacked in sequence along a first direction; the reverse-biased tunnel junction is located between adjacent active regions; the coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array includes a plurality of light emitting units distributed in a second direction, and there is a spacing region between adjacent light emitting units, and the second direction is perpendicular to the first direction; the refractive index guiding layer and the P-type electrode are located in the spacing region. In the present application, the refractive index guiding layer is added to the spacing region compared with the region where the light emitting units are located, so that the equivalent refractive index of the spacing region will be higher than the equivalent refractive index of the region where the light emitting units are located, forming a reverse waveguide structure. The light beam generated by the light emitting unit can propagate from the light emitting unit with a low equivalent refractive index to the spacing region with a high equivalent refractive index, that is, beam leakage is realized, so that the light beams emitted by adjacent light emitting units can meet in the spacing region between them, and coherent coupling occurs, and then phase locking is realized, that is, the phase difference between adjacent light beams is kept stable, thereby improving the beam quality and spectral quality, and a multi-junction VCSEL array with high power density, low divergence angle, and high spectral quality can be obtained. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 Shows a cross-sectional schematic diagram of a coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array provided by an embodiment of the present application;

[0030] Figure 2 Shows a flow schematic diagram of a preparation method of a coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array provided by an embodiment of the present application;

[0031] Figure 3 Shows another cross-sectional schematic diagram of a coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array provided by an embodiment of the present application;

[0032] Figure 4Shows a cross-sectional schematic diagram of another coherent coupled multi-junction cascaded vertical cavity surface emitting laser array provided by an embodiment of the present application;

[0033] Figure 5 Shows a cross-sectional schematic diagram of another coherent coupled multi-junction cascaded vertical cavity surface emitting laser array provided by an embodiment of the present application;

[0034] Figure 6 Shows a cross-sectional schematic diagram of another coherent coupled multi-junction cascaded vertical cavity surface emitting laser array provided by an embodiment of the present application;

[0035] Figure 7 Shows a cross-sectional schematic diagram of another coherent coupled multi-junction cascaded vertical cavity surface emitting laser array provided by an embodiment of the present application;

[0036] Figure 8 Shows a cross-sectional schematic diagram of another coherent coupled multi-junction cascaded vertical cavity surface emitting laser array provided by an embodiment of the present application;

[0037] Figure 9 Shows a cross-sectional schematic diagram of another coherent coupled multi-junction cascaded vertical cavity surface emitting laser array provided by an embodiment of the present application. Detailed implementation manners

[0038] To make the above objects, features, and advantages of the present application more obvious and understandable, the following will describe the detailed implementation manners of the present application in conjunction with the accompanying drawings.

[0039] In the following description, many specific details are set forth to fully understand the present application. However, the present application can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0040] Secondly, the present application will be described in detail with reference to the schematic diagrams. When detailing the embodiments of the present application, for the convenience of explanation, the cross-sectional views showing the device structure will be enlarged locally not in accordance with the general scale, and the schematic diagrams are only examples and should not limit the scope of protection of the present application herein. In addition, in actual production, three-dimensional spatial dimensions including length, width, and depth should be included.

[0041] For the convenience of understanding, the following will describe in detail a coherent coupled multi-junction cascaded vertical cavity surface emitting laser array and its manufacturing method provided by an embodiment of the present application in conjunction with the accompanying drawings.

[0042] Reference Figure 1As shown in the figure, it is a schematic cross-sectional view of a coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array provided by an embodiment of the present application. The coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array includes a heat sink substrate 1, an N-type electrode 2, an N-type mirror 3, multiple active regions, a reverse-biased tunnel junction, a refractive index guiding layer 6, a P-type mirror 7, and a P-type electrode 9 stacked in sequence along a first direction.

[0043] The first direction can be the vertical direction. The N-type electrode 2 can be used to connect to the positive pole of the power supply, and the P-type electrode 9 can be used to connect to the negative pole of the power supply. The mirror can be a Distributed Bragg Reflectors (DBR).

[0044] Current can be injected into the active region through the P-type electrode 9 and the N-type electrode 2, and this process stimulates the generation of electrons and holes. In the active region, these excited electrons and holes recombine, thereby releasing photons. The N-type mirror 3 and the P-type mirror 7 can jointly form an optical resonator in the first direction. This resonator can provide optical feedback for photons, so that after the photons are reflected multiple times in the cavity, the intensity of the light is significantly enhanced. When the carrier recombination rate in the active region reaches a certain threshold, the VCSEL begins to emit laser light.

[0045] Among them, the active region can include multiple layers. For example Figure 1 it includes three active regions, namely a first active region 41, a second active region 42, and a third active region 43. There is a reverse-biased tunnel junction between adjacent active regions. There is a first reverse-biased tunnel junction 51 between the first active region 41 and the second active region 42, and a second reverse-biased tunnel junction 52 between the third active region 43 and the second active region 42. The reverse-biased tunnel junction is a PN junction with a very high doping concentration in reverse bias. For a single active layer, the P region is on the top and the N region is on the bottom; but for the reverse-biased tunnel junction, its N region is on the top and the P region is on the bottom. When the power supply is turned on, the reverse-biased tunnel junction is reverse-biased. Due to the tunneling effect, the electrons injected into the first active layer can continue to tunnel through the reverse-biased tunnel junction into the next active layer, realizing the series connection between the active layers, so that the number of photons formed after injecting one electron is doubled, thereby greatly improving the slope efficiency and power conversion efficiency of the laser, and reducing the operating current and power consumption of the laser.

[0046] The coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array includes multiple light-emitting units distributed in a second direction, and there is a spacing region between adjacent light-emitting units. The second direction is perpendicular to the first direction. When the first direction is the vertical direction, the second direction can be the horizontal direction, and the light-emitting units are used to emit light beams. In the second direction, multiple light-emitting units can be arranged, and adjacent light-emitting units can be isolated by using the spacing region. For example Figure 1As shown, two light-emitting units and three spacer regions are shown in the coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array. The arrows in the figure indicate the light-emitting directions of the light-emitting units, and the light emits upward from the light-emitting holes of the light-emitting units.

[0047] Among them, the P-type electrode 9 is located in the spacer region, that is, the P-type electrode 9 is arranged in the spacer region. The refractive index guiding layer 6 is also located in the spacer region, and the refractive index guiding layer 6 is not arranged in the region where the light-emitting unit is located.

[0048] Since the ordinary multi-junction VCSEL array is an incoherent array, the light-emitting units are incoherent with each other, and optical field coherent coupling and phase locking will not be achieved, that is, the phase difference between two beams of light is not stable, which will lead to poor beam quality and spectral quality.

[0049] In this application, the equivalent refractive index is obtained by superimposing the products of the refractive indices and light intensity of each film layer. Since the spacer region has an additional refractive index guiding layer 6 compared with the region where the light-emitting unit is located, the equivalent refractive index of the spacer region will be higher than that of the region where the light-emitting unit is located, forming an anti-waveguide structure. The light beam generated by the light-emitting unit can propagate from the light-emitting unit with a low equivalent refractive index to the spacer region with a high equivalent refractive index, that is, beam leakage is achieved, so that the light beams emitted by adjacent light-emitting units can meet in the spacer region between them, undergo coherent coupling, and then achieve phase locking, that is, the phase difference between adjacent light beams is kept stable, thereby improving the beam quality and spectral quality, and a multi-junction VCSEL array with high power density, low divergence angle, and high spectral quality can be obtained.

[0050] In a possible implementation, the refractive index of the refractive index guiding layer 6 is greater than the refractive indices of the materials of the N-type mirror 3 and the P-type mirror 7.

[0051] That is to say, the refractive index of the refractive index guiding layer 6 is larger than the refractive index of the material used for the mirror. In this way, the refractive index guiding layer 6 will have a higher refractive index, and the difference in the equivalent refractive indices between the spacer region and the region where the light-emitting unit is located will be greater, which is more conducive to the propagation of the optical field to the spacer region with a higher equivalent refractive index, thereby further promoting optical field coherent coupling, achieving more stable phase locking, and achieving a smaller low divergence angle and higher spectral quality.

[0052] In a possible implementation, when the refractive index of the active region material is greater than the refractive indices of the materials of the N-type mirror 3 and the P-type mirror 7, the refractive index of the refractive index guiding layer 6 is greater than or equal to the refractive index of the quantum well material in the active region.

[0053] Specifically, when the refractive index of the active region is greater than that of the mirror, the refractive index of the refractive index guiding layer 6 material can be set not to be smaller than that of the quantum well material in the active region, so that the refractive index of the active region will be even greater, further increasing the difference in the equivalent refractive index between the spacer region and the region where the light-emitting units are located. The effect of optical field coherent coupling will be higher, the phase locking will be more stable, and even the coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array can operate in a single-mode state, achieving a smaller low divergence angle and higher spectral quality, and being applicable to scenarios with higher requirements for the laser beam to meet the scenario needs.

[0054] In a possible implementation, the coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array further includes an ion implantation region 8 located in the spacer region; the ion implantation region 8 includes multiple active regions, and the resistance value of the ion implantation region 8 is higher than a preset resistance value.

[0055] In the related art, ordinary multi-junction VCSEL arrays usually require multiple oxide layers to achieve good current confinement and optical field confinement. However, the presence of multiple oxide layers will introduce strong optical guiding, causing the array to operate in a multi-mode state, resulting in a divergence angle usually greater than 20°. Current confinement can be understood as confining the current to the region where the light-emitting units are located, and optical field confinement can be understood as confining the generated photons to the region where the light-emitting units are located, which will further inhibit the fusion between optical fields and cannot achieve phase locking.

[0056] In the embodiments of the present application, an ion implantation region 8 is formed in the spacer region. The ion implantation region 8 can at least involve multiple active regions. As an example, the ion implantation region 8 can include the film layers between the N-type mirror 3 and the P-type mirror 7, as Figure 1 shown. In the present application, by using the ion implantation region 8 to replace the multiple oxide layers, current confinement can also be achieved. The resistance value of the ion implantation region 8 will be relatively high, and the ion implantation region 8 can even be considered an electrically insulating region. Thus, the current will be confined within the region where the light-emitting units are located, but it will not confine the optical field, that is, the optical field can still leak into the spacer region, thereby achieving a low divergence angle of the beam.

[0057] In a possible implementation, the heat sink substrate 1 is a diamond heat sink substrate 1.

[0058] Since the spacing between adjacent light-emitting units is usually small, a large amount of heat generated in the light-emitting units will accumulate. In addition, due to the multiple layers in the active region, the heat conduction path will be lengthened, and the heat cannot be dissipated in time. That is to say, the thermal loss of the coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array is large, which will result in a low light extraction efficiency. Therefore, it is necessary to dissipate the heat in time.

[0059] The diamond heat sink substrate 1 has a high thermal conductivity, which can conduct the heat generated by the coherently coupled multi-junction cascaded vertical cavity surface emitting laser array out in time, improving the heat dissipation capacity of the coherently coupled multi-junction cascaded vertical cavity surface emitting laser array and enhancing the reliability of the coherently coupled multi-junction cascaded vertical cavity surface emitting laser array.

[0060] In a possible implementation, the material system of the coherently coupled multi-junction cascaded vertical cavity surface emitting laser array is InP-based, GaAs-based or GaN-based.

[0061] Specifically, in each film layer of the coherently coupled multi-junction cascaded vertical cavity surface emitting laser array, materials of InP-based, GaAs-based or GaN-based can be used, which can be specifically determined based on the emission wavelength of the laser.

[0062] When the emission wavelength is above 1300 nm, an InP-based material system can be used to construct the coherently coupled multi-junction cascaded vertical cavity surface emitting laser array. When the emission wavelength is within 650 - 1000 nm, a GaAs-based material system can be used to construct the coherently coupled multi-junction cascaded vertical cavity surface emitting laser array. When the emission wavelength is below 600 nm, a GaN-based material system can be used to construct the coherently coupled multi-junction cascaded vertical cavity surface emitting laser array.

[0063] In a possible implementation, the size of the spacer region in the second direction is determined based on the coupling mode.

[0064] Specifically, the coupling mode can include, for example, the in-phase mode and the anti-phase mode. In the in-phase mode, the phase difference between the light beams emitted by the two light-emitting units is 0. In the anti-phase mode, the phase difference between the light beams emitted by the two light-emitting units is π. By setting the width of the spacer region to an appropriate width, the corresponding coupling mode can be achieved. As an example, in some material structures, the larger the size of the spacer region, the larger the phase difference. In another material structure, the larger the size of the spacer region, the smaller the phase difference may be. In short, by setting the spacer region to have an appropriate size, the requirements for the coupling mode can be met.

[0065] Reference Figure 2 As shown, it is a schematic flowchart of a preparation method of a coherently coupled multi-junction cascaded vertical cavity surface emitting laser array provided by an embodiment of the present application, and the method may include the following steps.

[0066] S101, epitaxially form an N-type mirror 3, a multi-layer active region and an anti-biased tunnel junction on the epitaxial substrate 10 in sequence; the anti-biased tunnel junction is located between adjacent active regions.

[0067] Specifically, the N-type mirror 3, the multi-layer active region, and the reverse-biased tunnel junction can be formed on the epitaxial substrate 10 by means of Metal-organic Chemical Vapor Deposition (MOCVD) or Molecular Beam Epitaxy (MBE). Among them, the epitaxial substrate 10 can be, for example, an N-GaAs substrate, the N-type mirror 3 can be an lGaAs N-DBR mirror, the multi-layer active region can be an InGaAs / AlGaAs multi-quantum well multi-active region, and the reverse-biased tunnel junction can be a GaAs heavily doped multi-tunnel junction. Among them, the active region and the reverse-biased tunnel junction are alternately grown to achieve a reverse-biased tunnel junction between adjacent active regions. Refer to Figure 3 As shown, it is a cross-sectional view of a coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array provided by an embodiment of the present application.

[0068] S102, form a refractive index guiding layer 6 on the side of the multi-layer active region away from the N-type mirror 3.

[0069] Specifically, a refractive index guiding layer 6 is formed above the multi-layer active region, and the refractive index guiding layer 6 covers both the light-emitting unit and the spacer region.

[0070] S103, remove the refractive index guiding layer 6 in the region where the light-emitting unit is located, and retain the refractive index guiding layer 6 in the spacer region.

[0071] Specifically, in order to achieve different equivalent refractive indices, selective removal can be performed through a wet etching process to remove the refractive index guiding layer 6 in the light-emitting unit part, and only retain the refractive index guiding layer 6 in the spacer region. As Figure 4 shown, the refractive index guiding layer 6 is only located in the spacer region.

[0072] In addition, if the refractive index guiding layer 6 is in direct contact with the multi-layer active region, since the energy band widths of the two are not very different, it will cause carriers not to be confined in the active region. Therefore, a spacer layer can be formed before forming the refractive index guiding layer 6, and the energy band width of the spacer layer will be larger than that of the active region, so as to ensure that carriers can be confined in the active region and improve the light-emitting efficiency.

[0073] S104, form a P-type mirror 7 on the side of the refractive index guiding layer 6 away from the multi-layer active region.

[0074] Specifically, the P-type mirror 7 can be formed above the active region by means of epitaxial growth, and the material of the P-type mirror 7 can be AlGaAs. Refer to Figure 5 As shown, the P-type mirror 7 is formed.

[0075] S105. Form a P-type electrode 9 in the spacer region.

[0076] Specifically, referring to Figure 6 as shown, a P-type electrode 9 can be formed in the spacer region, and specifically, this electrode can be fabricated by using photolithography and evaporation processes.

[0077] S106. Remove the epitaxial substrate 10 and form an N-type electrode 2 on the side of the N-type mirror 3 away from the multi-layer active region.

[0078] Specifically, referring to Figure 8 as shown, the epitaxial substrate 10 can be removed by using substrate lift-off technology to obtain a coherent-coupled multi-junction cascade vertical cavity surface emitting laser array without the epitaxial substrate 10. Then, an N-type electrode 2 is formed on one side of the N-type mirror 3, referring to Figure 9 as shown.

[0079] S107. Form a heat sink substrate 1 on the side of the N-type electrode 2 away from the N-type mirror 3 to obtain a coherent-coupled multi-junction cascade vertical cavity surface emitting laser array.

[0080] Specifically, a new heat sink substrate 1 is formed on one side of the N-type electrode 2, thereby obtaining a complete coherent-coupled multi-junction cascade vertical cavity surface emitting laser array.

[0081] In a possible implementation, before removing the substrate 10, the method further includes performing multiple ion implantations on the multi-layer active region to form an ion implantation region 8; the implantation energy for each ion implantation is in the range of 200 keV - 380 keV, and the resistance value of the ion implantation region 8 is higher than a preset resistance value.

[0082] Specifically, referring to Figure 7 as shown, the elliptical region in the figure is the ion implantation region 8. After forming the P-type electrode 9, ion implantations can be performed on the spacer region in multiple times to obtain the ion implantation region 8. The implanted ions can be hydrogen ions, oxygen ions, nitrogen ions, etc.

[0083] As an example, after preparing an ion implantation mask, multiple ion implantations can be performed, and the implantation dose can be fixed at 1E15 cm -3 , and three implantations can be used, with the implantation energy being 250 keV, 315 keV, and 380 keV respectively each time to achieve electrical isolation.

[0084] In a possible implementation, the heat sink substrate 1 is a diamond heat sink substrate 1. Forming the heat sink substrate 1 on the side of the N-type electrode 2 away from the N-type mirror 3 to obtain a coherent-coupled multi-junction cascade vertical cavity surface emitting laser array can specifically be achieved by bonding the N-type electrode 2 to the diamond heat sink substrate 1 through a bonding technique to obtain a coherent-coupled multi-junction cascade vertical cavity surface emitting laser array.

[0085] Specifically, the N-type electrode 2 can be bonded to the diamond heat sink substrate 1 to obtain a complete coherent coupled multi-junction cascade vertical cavity surface emitting laser array. Refer to Figure 1 As shown, each layer of film is provided on the diamond heat sink substrate 1. The problem of heat accumulation in the coherent coupled multi-junction VCSEL array is solved, thereby further improving the power conversion efficiency and optical power density of the array.

[0086] As an example, the epitaxial substrate 10 is removed by using the substrate lift-off technique, then the N-type electrode 2 is grown, and after rapid thermal annealing treatment, the N-side of the array is bonded to the diamond heat sink by using the bonding technique, and finally a multi-junction cascade coherent coupled VCSEL array is prepared.

[0087] In the present application, the spacer region has an increased refractive index guiding layer compared to the region where the light emitting units are located. As a result, the equivalent refractive index of the spacer region will be higher than the equivalent refractive index of the region where the light emitting units are located, forming an anti-waveguide structure. The light beam generated by the light emitting unit can propagate from the light emitting unit with a low equivalent refractive index to the spacer region with a high equivalent refractive index, that is, beam leakage is achieved, so that the light beams emitted by adjacent light emitting units can meet in the spacer region between them, and coherent coupling occurs, thereby achieving phase locking, that is, the phase difference between adjacent light beams is kept stable, thereby improving the beam quality and spectral quality, and a multi-junction VCSEL array with high power density, low divergence angle, and high spectral quality can be obtained.

[0088] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and the key points of each embodiment are the differences from other embodiments. In particular, for the method embodiments, since they are basically similar to the device embodiments, they are described relatively simply, and the relevant parts can refer to the partial description of the device embodiments.

[0089] The above description is only a preferred embodiment of the present application. Although the present application has been disclosed above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present application by using the methods and technical contents disclosed above, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present application without departing from the technical solution of the present application still fall within the scope of the technical solution of the present application.

Claims

1. A coherent coupled multi-junction cascaded vertical cavity surface emitting laser array, characterized in that Comprising: A heat sink substrate, an N-type electrode, an N-type mirror, a multi-layer active region, a reverse-biased tunnel junction, a refractive index guiding layer, a P-type mirror, and a P-type electrode stacked in sequence along a first direction; the reverse-biased tunnel junction is located between adjacent active regions; The coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array includes a plurality of light emitting units distributed in a second direction, and there is a spacing region between adjacent light emitting units, and the second direction is perpendicular to the first direction; The refractive index guiding layer and the P-type electrode are located in the spacing region.

2. The coherent coupled multi-junction cascaded vertical cavity surface emitting laser array according to claim 1, wherein The refractive index of the refractive index guiding layer is greater than the refractive indices of the materials of the N-type mirror and the P-type mirror.

3. The coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array according to claim 2, characterized in that, When the refractive index of the active region material is greater than the refractive indices of the materials of the N-type mirror and the P-type mirror, the refractive index of the refractive index guiding layer is greater than or equal to the refractive index of the active region quantum well material.

4. The coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array according to claim 1, characterized in that, The coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array further includes an ion implantation region located in the spacing region; The ion implantation region includes the multi-layer active region, and the resistance value of the ion implantation region is higher than a preset resistance value.

5. The coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array according to claim 1, characterized in that, The heat sink substrate is a diamond heat sink substrate.

6. The coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array according to claim 1, characterized in that, The material system of the coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array is InP-based, GaAs-based or GaN-based.

7. The coherent coupled multi-junction cascaded vertical cavity surface emitting laser array according to claim 1, characterized in that, The size of the spacing region in the second direction is determined based on the coupling mode.

8. A method for preparing a coherently coupled multi-junction cascaded vertical cavity surface emitting laser array, characterized in that, The method includes: Epitaxially forming an N-type mirror, a multi-layer active region, and a reverse-biased tunnel junction on an epitaxial substrate in sequence; the reverse-biased tunnel junction is located between adjacent active regions; Forming a refractive index guiding layer on a side of the multi-layer active region away from the N-type mirror; Removing the refractive index guiding layer in the region where the light emitting unit is located, and retaining the refractive index guiding layer in the spacing region; Forming a P-type mirror on a side of the refractive index guiding layer away from the multi-layer active region; Forming a P-type electrode in the spacing region; Removing the epitaxial substrate, and forming an N-type electrode on a side of the N-type mirror away from the multi-layer active region; Forming a heat sink substrate on a side of the N-type electrode away from the N-type mirror to obtain the coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array.

9. The preparation method according to claim 8, characterized in that, Before removing the epitaxial substrate, the method further includes: Performing multiple ion implantations on the multi-layer active region to form an ion implantation region; the implantation energy for each ion implantation is in the range of 200 keV - 380 keV, and the resistance value of the ion implantation region is higher than a preset resistance value.

10. The preparation method according to claim 8, characterized in that, The heat sink substrate is a diamond heat sink substrate, and forming the heat sink substrate on a side of the N-type electrode away from the N-type mirror to obtain the coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array includes: Bonding the N-type electrode and the diamond heat sink substrate through a bonding technique to obtain the coherent-coupled multi-junction cascaded vertical cavity surface emitting laser array.

Images