Metasurface unit, semiconductor laser and preparation method

Abstract

The invention relates to the technical field of semiconductor lasers, in particular to a metasurface unit, a semiconductor laser and a preparation method. The metasurface unit comprises a first column body and a second column body, wherein the first column body and the second column body are sequentially arranged from bottom to top; wherein the first column body is a rectangular photonic crystal column, and the rectangular photonic crystal column is used for suppressing radial and angular high-order modes of output light; the tubular column is used for further controlling the light beam of the output light, so that the single-mode output efficiency of the output light is improved. According to the embodiment, radial and angular high-order modes of output light can be effectively suppressed through the diffraction characteristic of the rectangular-column photonic crystal. And the super lens formed by the tubular column is arranged on the rectangular column, the focusing capability of the super lens is utilized to further improve the beam quality, and the gradient design of the curvature radius of the lens enables beam behaviors in different areas to be accurately controlled.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor lasers, and in particular to a metasurface unit, a semiconductor laser and a preparation method thereof. Background Art

[0002] At present, high-speed modulated VCSEL is the research focus of the laser industry. At present, VCSEL with 25GHz bandwidth has been relatively mature, but there are still many challenges in how to further improve the performance of VCSEL. For example, the output light of VCSEL has high-order multi-transverse modes, and the existence of high-order transverse modes will reduce the signal-to-noise ratio and affect the quality of the output light.

[0003] In the process of realizing the present invention, the inventors found that: currently, to control the output beam quality of VCSEL lasers, an external beam controller is often required, which requires some space for the laser and increases the cost. It is difficult to control the output beam of semiconductor lasers without reducing the space and cost. Summary of the invention

[0004] In view of the above problems, the present invention is proposed to provide a metasurface unit, a semiconductor laser and a preparation method that overcome the above problems or at least partially solve the above problems.

[0005] In a first aspect, an embodiment of the present invention provides a metasurface unit for a light output port of a semiconductor laser, characterized in that the metasurface unit comprises: a first column and a second column, wherein the first column and the second column are arranged sequentially from bottom to top; Wherein, the first column is a rectangular photonic crystal column, and the rectangular photonic crystal column is used to suppress radial and angular high-order modes of the output light; The tubular column is used to further control the light beam of the output light, thereby improving the single-mode output efficiency of the output light.

[0006] Furthermore, the side length of the cross section of the first column is controlled to be 0.15-0.35um, and the height is controlled to be 0.15-0.3um; the outer diameter of the second column is controlled to be 0.05-0.2um, and the inner diameter is controlled to be 0.04-0.1um.

[0007] Furthermore, the first column and the second column include Si 3 N 4 or TiO 2 At least one is made.

[0008] A second aspect also discloses a semiconductor laser, comprising: a semiconductor laser light emitting structure having a vertical cavity surface emitting laser structure; The metasurface unit, the metasurface unit array forms a metasurface, the metasurface is arranged at the light output port of the semiconductor laser light-emitting structure, and the coupling layer is arranged between the metasurface unit array and the semiconductor laser light-emitting structure; The metasurface unit array is a uniform annular array structure extending from the center of the light output port to the edge, and an array structure of n metasurface units is formed around any metasurface unit as the center.

[0009] Furthermore, the array structure is configured such that the distance between each array ring in the annular array gradually increases from the center position of the light output port to the edge.

[0010] Furthermore, the first column of the metasurface unit is a rectangular photonic crystal column, and the rectangular photonic crystal column is used to rotate clockwise to radially control the output light.

[0011] Furthermore, the coupling layer is SiO 2 layer, and the SiO 2 The thickness of the layer was controlled to be 15-25 nm.

[0012] Furthermore, in the metasurface unit array, the second column is configured as a structure in which the diameter gradually decreases from the center of the light output port toward the outside.

[0013] The third aspect also discloses a method for preparing a semiconductor laser, the steps comprising: A coupling layer is plated on the semiconductor laser light emitting structure by a magnetron sputtering process; A mask layer is printed on the upper side of the coupling layer, wherein the mask layer is provided with a first column pattern corresponding to the light output port, and then a filling column is plated inside the first column pattern to obtain a column layer; cleaning the mask layer on the pillar layer using a solvent, thereby leaving the filled pillars; The upper part of the filling column is etched out into a second column by an etching process to obtain a semiconductor laser with a super surface.

[0014] Furthermore, after the coupling layer is plated on the semiconductor laser light-emitting structure, the photoresist is printed on the coupling layer through a two-photon polymerization process, thereby obtaining the mask layer on the coupling layer, and the mask layer sets a first column pattern at the position corresponding to the light output port, and the first column pattern is a rectangular pattern.

[0015] The beneficial effects of the above technical solution provided by the embodiment of the present invention include at least: In an embodiment of the present invention, a metasurface unit is provided, which can effectively suppress the radial and angular high-order modes of the output light through the diffraction characteristics of the photonic crystal of the rectangular column. The upper surface of the rectangular column is provided with a superlens formed by a tubular column, and the focusing ability of the superlens is used to further improve the beam quality. The gradual curvature radius design of the lens enables the beam behavior in different areas to be accurately controlled. In the embodiment, the output light beam optimization control and mode selection are realized through the composite structure of the two column structures, which effectively affects the high-order modes and further improves the single transverse mode output efficiency of the laser.

[0016] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0017] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0019] Figure 1 is a semiconductor laser of an embodiment; Figure 2 is a schematic diagram of a supersurface unit according to a first embodiment of the present invention; Figure 3 is a schematic diagram of a metasurface according to a first embodiment of the present invention; Figure 4 is a schematic diagram of a metasurface according to a second embodiment of the present invention; Figure 5 The present invention Figure 4 A schematic diagram from another perspective; Figure 6 A semiconductor laser according to an embodiment of the present invention; Figure 7 is a schematic diagram of a two-photon polymerization device for printing a mask layer of the present invention; Figure 8 is the spot diagram of the output light of the semiconductor laser without using the present metasurface; Fig. 9 is a spot diagram of the output light of the semiconductor laser of the present invention; Fig.10 is a comparison diagram of the intensity distribution of the output light spot of a semiconductor laser according to an embodiment of the present invention; Fig.11 is a flow chart of a method for preparing a semiconductor laser according to an embodiment of the present invention; Fig.12 1 is a schematic diagram of a super surface viewed from above according to an embodiment of the present invention.

[0020] Indicated in the figure: 100. Semiconductor laser; 110. Semiconductor laser light-emitting structure; 120. Beam shaper; 121. Metasurface; 101, substrate; 102, N-type DBR portion; 103, N-electrode; 104, active region layer; 105, P-type DBR portion; 106, P-electrode; 107, metasurface unit; 108, coupling layer; 1070, first column; 1071, second column; 1072, first circular array; 1073, second circular array; 1074, third circular array. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0022] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present application and simplifying the description, 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 cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0023] In this application, the word "exemplary" is used to mean "used as an example, illustration, or description." Any implementation described in this application as "exemplary" is not necessarily to be construed as being more preferred or advantageous than other implementations. The following description is given to enable any technician in the field to implement and use the present application. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the present application can be implemented without using these specific details. In other examples, well-known structures and processes will not be elaborated in detail to avoid obscuring the description of the present application with unnecessary details. Therefore, the present application is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed in the present application.

[0024] Beam shaping is a process that uses beam steering technology to change the shape and characteristics of a beam. A beam shaper can transform a Gaussian incident laser beam into a circular, rectangular, square, straight or other custom shapes.

[0025] Typical applications of beam shapers include: optical path design and manufacturing of laser lenses such as laser welding, laser cutting, laser marking, laser printing, laser drilling, laser scribing, laser ablation, laser melting, laser rapid prototyping, laser 3D printing, as well as miniLED welding maintenance, LDI shaping light source, laser medicine, aesthetic laser (landscape) and entertainment laser, etc.

[0026] See attached Figure 1 , schematically showing a semiconductor laser 100 according to an example embodiment. Figure 1 , an embodiment of a semiconductor laser 100 may include a substrate 101, a semiconductor laser light emitting structure, and a beam shaper 120 disposed at a light output end. The beam shaper 120 is disposed on one side of the semiconductor laser light emitting structure. The semiconductor laser light emitting structure may be a VCSEL. The beam shaper 120 may include a metasurface 121. For example, the metasurface 121 may include an array of nano-metasurface units 107 (e.g., a plurality of nano-metasurface units 107) as an example of a beam shaper structure. The metasurface 121 includes the same type of material as the material forming the semiconductor laser light emitting structure.

[0027] The metasurface 121 is a sub-wavelength artificial nanostructure film, which can modulate the incident light according to the metasurface unit 107 thereon. The metasurface unit 107 includes a fully dielectric or plasma nanoantenna, which can directly control the phase, amplitude, polarization and other characteristics of the light. The metasurface units 107 are arranged in an array, and the metasurface units 107 can be regular hexagons and / or squares. The center position of each metasurface unit 107 is a regular hexagonal and square metasurface structure unit arrangement diagram. It should be understood that the metasurface unit 107 can also be other shapes, and the position of the nanostructure setting can also adopt other positions other than the center / vertex position.

[0028] As an embodiment, the semiconductor laser light emitting structure may include an N-type DBR portion 102, an active region layer 104, and a P-type DBR portion 105 on a substrate 101. The semiconductor laser light emitting structure may include a III-V compound semiconductor material. For example, the semiconductor laser light emitting structure may include a GaAs-based compound semiconductor material. For example, the semiconductor laser light emitting structure may include at least one of GaInP, AlGaInP, GaAs, GaInAs, AlGaAs, and AlGaInAs.

[0029] As an example embodiment, the substrate 101 may be a semiconductor substrate 101. For example, a Si substrate, a GaAs substrate, etc. may be used as the substrate. If necessary, a buffer layer and a seed layer whose material for forming the semiconductor laser light emitting structure is lattice-matched with the substrate 101 may be provided between the substrate 101 and the semiconductor laser light emitting structure.

[0030] The active region layer 104 may include one or more quantum wells or quantum dots.

[0031] The N-electrode 103 may be disposed on a portion of the N-type DBR portion 102. The active region layer 104 may be provided in a region of the N-type DBR portion 102 that is not occupied by the N-electrode 103. The P-electrode 106 may be disposed on a portion of the P-type DBR portion 105.

[0032] Figure 1 The semiconductor laser light emitting structure shown is only an example and the scope of the present invention is not limited to Figure 1 The semiconductor laser light emitting structure shown in FIG. may include Figure 1 Various additional components / layers not shown.

[0033] In example embodiments, the emitting semiconductor laser 100 has a metasurface 121 , for example, the semiconductor laser light emitting structure may have a VCSEL structure that generates laser light.

[0034] In an example embodiment, the beam shaper 120 including the metasurface 121 is arranged at a light output side relative to the active region layer 104, for example, at a side opposite to the N-type DBR portion 102 relative to the active region layer 104, and the metasurface 121 may be used as an upper reflector layer forming a cavity of a VCSEL by pairing with the P-type DBR portion 105.

[0035] The metasurface 121 may include an array of multiple metasurface units 107. For example, the array of multiple metasurface units 107 may be arranged in an area on the P-type DBR portion 105 that is not occupied by the P electrode 106. The metasurface 121 may also perform a feedback function of the cavity of the semiconductor laser light emitting structure, i.e., VCSEL.

[0036] Figure 1 An example embodiment of a metasurface is shown. Figure 1 , the metasurface 121 may include a plurality of metasurface units 107 spaced apart from each other. The plurality of metasurface units 107 may form an array of the metasurface units 107.

[0037] Before describing the embodiments of the present invention in detail, the design concept of the present invention is briefly described below. Figure 4 As shown, the present invention designs a metasurface 121, and the metasurface unit 107 includes a first cylinder 1070 and a second cylinder 1071, wherein the first cylinder 1070 is an elliptical cylinder, and the second cylinder 1071 is a circular cylinder. The upper and lower layers of the metasurface unit 107 have different structural designs, that is, the metasurface unit 107 can be used for a dual-axis structure to regulate the state of the light beam, thereby effectively suppressing the radial and angular high-order modes of the output light of the laser, so as to focus the light spot and achieve single transverse mode focusing and high-efficiency output of the laser.

[0038] The inventor of this application is continuing to study how to effectively solve the problem of unsatisfactory control of the current metasurface beam quality. The inventor's research at least includes: how to control the output beam quality of semiconductor lasers, suppress the radial and angular high-order modes of the output light through the metasurface structure, and improve the quality of the light spot. After a lot of repeated research, the inventor proposed the metasurface and semiconductor laser of this application.

[0039] Refer to the attached Figure 2 As shown, in an embodiment of the present invention, a metasurface unit is provided, which is used for the light output port of a semiconductor laser 100, and the metasurface unit includes: a first column 1070 and a second column 1071, wherein the first column 1070 and the second column 1071 are arranged sequentially from bottom to top; Wherein, the first column 1070 is a rectangular photonic crystal column, which is used to suppress radial and angular high-order modes of the output light; The tubular column is used to further control the light beam of the output light, thereby improving the single-mode output efficiency of the output light.

[0040] It can be understood that in the embodiment, the metasurface element includes a first column 1070 and a second column 1071, wherein the first column 1070 is a rectangular column, and the second column 1071 is a tubular column. The metasurface element is designed with different upper and lower layers, that is, the metasurface element can be used in a dual-axis structure. Through the combination of photonic crystals and superlenses, the quality of the light beam is regulated, thereby effectively suppressing the radial and angular high-order modes of the output light of the laser, thereby reducing high-order transverse modes and ultimately improving the quality of the output light beam.

[0041] The tubular column described here can be considered as a column with a circular cross-section.

[0042] At the same time, through the diffraction characteristics of the photonic crystal of the rectangular column, the radial and angular high-order modes of the output light can be effectively suppressed, and the light beam can be focused on the axis. The upper part of the rectangular column is set as a super lens formed by a tubular column, and the focusing ability of the super lens is used to further improve the beam quality. In the embodiment, the output light beam optimization control and mode selection are realized through the composite structure of the two column structures, which effectively affects the high-order modes and further improves the laser single transverse mode output efficiency.

[0043] It should be pointed out that photonic crystal is an artificial periodic dielectric structure with photonic bandgap characteristics, and its diffraction characteristics are mainly generated by the periodic arrangement of dielectric constants modulating electromagnetic waves.

[0044] A superlens is a two-dimensional planar lens structure made of an optical element that focuses light on a metasurface 121 (a planar two-dimensional (2D) c metamaterial with subwavelength thickness). The design principle of a superlens is based on two special features of the metasurface: the choice of metasurface phase distribution and the geometric design of nanoscale structures. The control of light wave characteristics (including phase, amplitude and polarization) can be achieved through the design and manufacture of geometric structures, and the profile, position and angle of the subwavelength structure can be adjusted to control the focusing and imaging characteristics of the superlens. When the height of the micro-nano structure is fixed, it can be adjusted by the shape, size and structural unit period of the micro-nano structure. The superlens designed based on the propagation phase principle is usually composed of isotropic micro-nano structures and has a high degree of symmetry.

[0045] In the embodiment, by combining the metasurface of a rectangular photonic crystal and a circular ring column, and arraying the combined structure into the desired metasurface, the light beam can be regulated by the photonic crystal, and the radial and angular high-order modes of the output light of the laser can be effectively suppressed, thereby reducing the high-order transverse modes, improving the signal-to-noise ratio, and ultimately improving the beam intensity of the output light.

[0046] Refer to the attached Figure 3 As shown in the embodiment, the side length of the cross section of the first column 1070 is controlled to be 0.15-0.35um, and the height is controlled to be 0.15-0.3um; the outer diameter of the second column 1071 is controlled to be 0.05-0.2um, and the inner diameter is controlled to be 0.04-0.1um. The first column 1070 and the second column 1071 include Si 3 N 4 or TiO 2 At least one is made.

[0047] In one embodiment, the first body is a square with a cross-sectional side length of 0.2 um, that is, Si 3 N 4 In other embodiments, the first body is a rectangular cross-section with a long side of 0.3um and a short side of 0.2um, that is, Si 3 N 4 In some other embodiments, the first body is a square with a side length of 0.15um in the cross section, that is, TiO 2 of square cylinder.

[0048] The cross section described here is the cross section of the parallel light output port.

[0049] Based on the same inventive concept, refer to the attached Figure 4 and 6 As shown, a semiconductor laser 100 includes: a semiconductor laser light emitting structure 110 having a vertical cavity surface emitting laser structure; The metasurface unit, the metasurface unit array forms a metasurface 121, the metasurface 121 is arranged at the light output port of the semiconductor laser light-emitting structure 110, and the coupling layer 108, the coupling layer 108 is arranged between the metasurface unit array and the semiconductor laser light-emitting structure 110; The metasurface unit array is a uniform annular array structure from the center of the light output port to the edge, and an array structure of n metasurface units is formed around any metasurface unit as the center, where n represents the number of arrays, including 5-8.

[0050] In the embodiment, the radial and angular high-order modes of the output light are effectively suppressed by utilizing the diffraction characteristics of the photonic crystal, and the focusing ability of the super lens is further used to improve the beam quality, so that the beam behavior can be precisely controlled. In the embodiment, the beam optimization control and mode selection of the output light are realized through the composite structure of the two column structures, which effectively affects the high-order modes and further improves the single transverse mode output efficiency of the laser.

[0051] Refer to the attached Figure 5 As shown, in the embodiment, the metasurface unit array forms a metasurface 121 to obtain the control function of the light beam. The embodiment also includes a plurality of small annular array structures in the metasurface unit array. The plurality of small annular array structures refers to a ring array structure formed around any one of the metasurface units. In the embodiment, by arranging a plurality of small arrays, the control of the light beam is faster and more accurate, and the control of light at various positions is realized.

[0052] Refer to the attached Figure 3 As shown, in some embodiments, the metasurface unit array is a metasurface unit arranged at the center of the light output port, and a ring of 6 metasurface units in an annular array are arranged around the center. Figure 5 n1 and n2, and in the metasurface unit array, except for the edge positions of the array, a circle of 6 metasurface units is formed around any one of the metasurface units as the center; in other embodiments, the metasurface unit array is a circle of 5 metasurface units arranged around the center, and in the metasurface unit array, except for the edge positions of the array, a circle of 5 metasurface units is formed around any one of the metasurface units as the center; in some further embodiments, the metasurface unit array is a circle of 7 metasurface units arranged around the center, and in the metasurface unit array, except for the edge positions of the array, a circle of 7 metasurface units is formed around any one of the metasurface units as the center.

[0053] Refer to the attached Figure 5 As shown, in a further embodiment, the array structure is configured such that the distance between each array ring in the annular array gradually increases from the center position of the light output port to the edge.

[0054] It can be understood that the metasurface 121 is a ring array formed by a metasurface unit array, and the specific ring array is composed of multiple separate ring arrays, and is evenly distributed from the center to the edge. The distance between each separate ring array is different, and specifically from the center to the edge, the distance between the separate ring arrays gradually increases. By regularly setting the array structure formed by the metasurface 121, the output efficiency of the speed of light is effectively improved.

[0055] In one embodiment, the metasurface array is configured to include a first circular array 1072, a second circular array 1073, and a third circular array 1074 in sequence from the center of the light output port to the edge. The distance between the center of the light output port and the first circular array 1072 is 0.3um, the distance between the first circular array 1072 and the second circular array 1073 is 0.6um, and the distance between the second circular array 1073 and the third circular array 1074 is 0.9um, and the array is formed in this order. It can be considered that the distance between the individual circular arrays gradually increases from the center to the edge in the range of 0.25-0.35um.

[0056] Refer to the attached Figure 4 and 5 As shown, in a further embodiment, the first column 1070 of the metasurface unit is a rectangular photonic crystal column, and the rectangular photonic crystal column is used to rotate clockwise to radially and angularly control the output light and focus the light beam.

[0057] It can be understood that in order to achieve radial control of the light beam at a certain angle, the metasurface 121 array formed by the metasurface units described in the embodiment, one of the metasurface units is set at the center point of the light output port, and the other metasurface units are set to be deflected at an angle relative to the metasurface unit at the center point, so that the rectangular photonic crystal can control the angular direction of the light beam and focus the light beam to the center at the same time, so that the quality of the light beam is high.

[0058] It should be pointed out that the deflection angle can be considered as the deflection on the array structure, which enables the array to have the function of regulating the angular and radial directions of the light beam. The deflection on the array structure can be considered as the structural deflection of the specific metasurface unit in the array, or it can be considered as the angle deflection performed by setting the array arrangement of a part of the metasurface units in the array. The main purpose is to enable the rectangular photonic crystal to focus the light beam toward the center, so that the quality of the light beam is high.

[0059] In some embodiments, the first column 1070 of the metasurface unit is a rectangular photonic crystal column, and, except for the rectangular photonic crystal at the center point, the columns of other rectangular photonic crystal columns in the array are rotated 45° clockwise; in other embodiments, the first column 1070 of the metasurface unit is a rectangular photonic crystal column, and, except for the rectangular photonic crystal at the center point, the columns of other rectangular photonic crystal columns in the array are rotated 30° clockwise; in still other embodiments, the first column 1070 of the metasurface unit is a rectangular photonic crystal column, and, except for the rectangular photonic crystal at the center point, the columns of other rectangular photonic crystal columns in the array are rotated 50° clockwise.

[0060] For example, see the attached Fig.12 , the supersurface unit at the center of the coupling film is used as a reference. Relative to the supersurface unit at this position, the supersurface units at other positions are all rotated by an angle θ, and this angle θ is controlled to be 30-60°. It can be considered that the supersurface unit at the center of the coupling film establishes a first reference coordinate perpendicular to the rectangular side, and the supersurface units at other positions establish a second reference coordinate perpendicular to the rectangular side, and the second reference coordinate is rotated clockwise by an angle θ relative to the first reference coordinate. It can be understood that, except for the supersurface unit at the center of the coupling film, the other supersurface units are uniformly rotated clockwise by an angle, and it can also be considered that the first column 1070 is a rectangular photonic crystal column rotated by an angle.

[0061] See attached Figure 4 As shown, in the embodiment further, in the metasurface unit array, the second column 1071 is configured to have a structure in which the diameter gradually decreases from the center position of the light output port toward the outside.

[0062] It can be understood that in order to make the second column 1071 array into a super lens, the light beam is controlled by the super lens, and the array of the second column 1071 is set as a gradual array, so that the gradual mode of the super lens can be realized, that is, the output light beam is controlled by the super lens gradual mode. Specifically, the outer diameter of the second column 1071 in the array is set to a structure that gradually decreases from the center of the array to the outside, and it can be considered that the light output port of the semiconductor laser 100 gradually changes to the edge. For each circle arranged toward the edge in the annular array, the outer diameter of the second column 1071 is correspondingly reduced by one number, so that the radius of curvature of the super lens at the second column 1071 array site presents a gradual form, thereby realizing the control of the light beam, that is, by designing the radius of curvature of the lens as a gradual structure, the light beam behavior in different regions can be accurately controlled, so as to ensure the output light beam intensity and improve the output efficiency.

[0063] For example, in the embodiment, the metasurface 121 array is arranged to include a first circular array 1072, a second circular array 1073 and a third circular array 1074 in sequence from the center of the light output port to the edge. Among them, the outer diameter of the second cylinder 1071 at the center of the light output port is 0.1um, the inner diameter is 0.06um, and the height is 2um; the first circular array 1072 has six second cylinders 1071, the outer diameter of the six second cylinders 1071 is 0.09um, the inner diameter is 0.06um, the height is 2um, and the distance between the six second cylinders 1071 is 0.3um; the second circular array 1073 has twelve second cylinders 1071, the outer diameter of the twelve second cylinders 1071 is 0.08um, the inner diameter is 0.06um, the height is 2um, and the distance between the twelve second cylinders 1071 is 0.3um; the third circular array 1074 has eighteen second cylinders 1071, the outer diameter of the eighteen second cylinders 1071 is 0.075um, the inner diameter is 0.05um, the height is 2um, and the distance between the eighteen second cylinders 1071 is 0.3um; and the array is formed in this way.

[0064] In an embodiment, the second columns 1071 are arrayed into a superlens, and the second columns 1071 are set to a gradient structure, that is, the curvature radius of the superlens is gradually designed, so that the light beam behavior in different areas can be accurately controlled, further improving the light beam quality.

[0065] In a further embodiment, a coupling layer 108 is provided between the metasurface 121 and the semiconductor laser 100 light emitting structure, and the coupling layer 108 is used to reduce the optical coupling between the two. The coupling layer 108 is SiO 2 Piece.

[0066] Based on the same inventive concept, a method for preparing a super surface is also disclosed. Fig.11 As shown, the steps include: Step S001: a coupling layer 108 is plated on the semiconductor laser light emitting structure 110 by a magnetron sputtering process.

[0067] By setting a coupling layer 108 between the metasurface 121 and the semiconductor laser light-emitting structure 110, specifically at the output hole position of the output light of the semiconductor laser light-emitting structure 110, the coupling layer 108 can effectively reduce the optical coupling between the semiconductor laser light-emitting structure 110 and the metasurface 121, and at the same time act as a stress relief layer.

[0068] In the embodiment to be explained, the coupling layer 108 is SiO 2 layer, and the SiO 2 The thickness of the layer was controlled to be 15-25 nm.

[0069] In some embodiments, SiO is directly plated on the patterned VCSEL wafer using a magnetron sputtering process. 2 The thin film layer, wherein the SiO 2 The thickness of the film layer is controlled to be 20 nm. In other embodiments, SiO is directly plated on the patterned VCSEL wafer using a magnetron sputtering process. 2 The thin film layer, wherein the SiO 2 The thickness of the film layer is controlled to be 16 nm. In some embodiments, SiO is directly plated on the patterned VCSEL wafer using a magnetron sputtering process. 2 The thin film layer, wherein the SiO 2 The thickness of the film layer is controlled to be 24 nm.

[0070] It is understandable that the coupling layer 108 may be replaced by another material.

[0071] Step S002: a mask layer is printed on the upper side of the coupling layer 108, the mask layer is provided with a first column pattern corresponding to the light output port, and then a filling column is plated inside the first column pattern to obtain a column layer; In a further embodiment, after the coupling layer 108 is plated on the semiconductor laser light-emitting structure, photoresist is printed on the coupling layer 108 by a two-photon polymerization process, thereby obtaining the mask layer on the coupling layer 108, and the mask layer sets a first columnar pattern at the position corresponding to the light output port, and the first columnar pattern is a rectangular pattern.

[0072] For example, see the attached Figure 7 The figure shows a schematic diagram of a two-photon polymerization device printing a mask layer. After the coupling layer 108 is plated, the semiconductor laser light-emitting structure is placed on a fixed frame of the two-photon polymerization device. The positive photoresist is 3D printed on the upper side of the coupling layer 108 using a two-photon polymerization process, so that a layer of positive photoresist is formed on the upper side of the coupling layer 108. Here, the upper side of the coupling layer 108 can be considered as the side away from the semiconductor laser light-emitting structure. And when printing, at the position corresponding to the light output port of the semiconductor laser light-emitting structure 110, a first column pattern is reserved for design. The first column pattern is a cross-sectional pattern of the first column 1070. Here, the first column pattern is a rectangular pattern. Other structures are not excluded. As long as the diffraction characteristics of the photonic crystal are used to effectively suppress the radial and angular high-order modes of the light beam, it can be the same as the present application.

[0073] The rectangular pattern here can be considered as a hollow column structure, that is, the rectangular pattern is surrounded by photoresist, and a rectangular hollow column is formed by solidifying the photoresist.

[0074] Next, the filler is coated into the first column pattern by using a magnetron sputtering process. When coating the first column pattern, Si 3 N 4 or TiO 2 One of the materials is coated to obtain a filling column at a reserved position of the photoresist layer, thereby obtaining a column layer.

[0075] Step S003: using a solvent to clean the mask layer on the pillar layer, thereby leaving the filling pillars.

[0076] It can be understood that in the embodiment, a mask layer is used to assist in manufacturing a filling column having a first column 1070, and then the mask layer is removed to obtain the desired filling column on the isolation layer. By further processing the filling column, a second column 1071 can be obtained on the first column 1070, thereby obtaining a metasurface 121, and the light beam can be controlled by the metasurface 121. Such a design process makes it easier to manufacture the metasurface 121 and reduces the difficulty of the process.

[0077] The mask layer on the semiconductor laser light emitting structure 110 is cleaned with a solvent, thereby leaving a filling column. The filling column is further processed to obtain a semiconductor laser 100 having the above-mentioned metasurface 121.

[0078] In actual work, an acetone solution is used to dissolve the positive photoresist. Specifically, the semiconductor laser 100 light-emitting structure is placed in an ultrasonic device and an appropriate acetone solution is added. When cleaning, the cleaning power of the ultrasonic device is set to 20-25W, and the cleaning time is controlled to 5-10 minutes, so that the photoresist printed on the semiconductor laser light-emitting structure 110 is effectively cleaned. The remaining filling column is the first column 1070 of the super surface unit, which is prepared for the next step. The height of the first column 1070 here usually includes the height of the second column 1071, that is, the next station is reserved to process the upper part of the filling column into the second column 1071.

[0079] In a further embodiment, the filler comprises Si 3 N 4 or TiO 2 One of them.

[0080] For example: In some embodiments, the thickness of the column layer is controlled to be 0.4um, the height of the column filling is 0.4um, and the filler is TiO 2 Filling is performed and finally TiO 2In other embodiments, the thickness of the column layer is controlled to be 0.3um, the height of the filling column is 0.3um, and the filler is Si 3 N 4 Filling to obtain Si 3 N 4 In some other embodiments, the thickness of the column layer is controlled to be 0.5um, the height of the column filling is 0.5um, and the filler is Si 3 N 4 Filling to obtain Si 3 N 4 Made of rectangular cylinder.

[0081] It should also be pointed out that in this embodiment, the super surface 121 is configured as the tubular column, the square column and the SiO 2 In another embodiment, the super surface 121 can also be designed as the tubular column, rectangular column and SiO 2 The preparation method refers to the above steps and will not be described here.

[0082] At the same time, the heights of the first column 1070 and the second column 1071 can be set to the same height or different heights. In addition, the first column 1070 and the second column 1071 can be made of the same material, and at the same time, the first column 1070 and the second column 1071 can also be made of different materials. In an embodiment, the radial and angular high-order modes of the output light are effectively suppressed by utilizing the diffraction characteristics of the photonic crystal, and the beam quality is further improved by utilizing the focusing ability of the superlens. The gradual curvature radius design of the lens enables the beam behavior in different areas to be precisely controlled. In an embodiment, the output light beam optimization control and mode selection are realized through the composite structure of the two column structures, which effectively affects the high-order modes and further improves the single transverse mode output efficiency of the laser.

[0083] Step S004 : using an etching process to etch out a second column 1071 from the upper portion of the filling column, thereby obtaining a semiconductor laser 100 having a supersurface 121 .

[0084] In the embodiment, a mask having a tubular structure is manufactured. The mask here can refer to conventional preparation methods and will not be described here. A pattern of a supersurface unit array design is designed on the mask. Specifically, the pattern on the mask includes a plurality of circular ring arrays, and the outer diameters of the circular rings in the circular array are arranged to gradually decrease from the center of the array to the outside, and can be considered to change from the center of the mask to the edge. Specifically, for each circle of circular rings arranged toward the edge in the array, the outer diameter of the circular rings is correspondingly reduced by one number, and the distance between each circular ring in each circle is 0.3um.

[0085] Then, the upper part of the filling column is etched by the pattern on the mask through a photolithography process to obtain a first column 1070 with a rectangular structure at the bottom and a second column 1071 with a tubular column at the top, thereby obtaining the required supersurface 121 combining the photonic crystal and the superlens.

[0086] In the embodiment, a rectangular photonic crystal and a circular column superlens are combined, and the combined structure is arrayed to form the required supersurface, that is, the diffraction characteristics of the rectangular column photonic crystal can effectively suppress the radial and angular high-order modes of the output light, and focus the light beam on the axis. The top of the rectangular column is set as a superlens formed by a tubular column, and the focusing ability of the superlens is used to further improve the beam quality, thereby reducing the high-order transverse mode and ultimately improving the output light quality.

[0087] See attached Figure 3 As shown in an example, the metasurface 121 is obtained by a plurality of metasurface unit arrays, the heights of the first column 1070 and the second column 1071 of the metasurface 121 are set to 200 nm, and the first column 1070 is a TiO 2 The second column 1071 is a TiO 2 Ring column.

[0088] See attached Figure 5 As shown, the annular array arrangement of the metasurface units is centered on the center of the light output port, and the distance from the center of each ring of the annular array increases by 0.3um from the center to the outside, and the interval between the metasurface units in each ring is 0.3um. The first body has a deflection angle of 45 degrees clockwise, so that 6*10 photonic crystal super lenses are evenly arranged; the cross-section of the second column 1071 is circular, with an outer diameter of 0.1um and an inner diameter of 0.06um. The second column 1071 is set to a structure in which the diameter gradually decreases from the center of the light output port to the outside, so that 6*10 lenses are evenly arranged.

[0089] See attached Figure 8As shown, by observing the light spot output by the 850nm laser without the metasurface 121, it can be seen that the light spot is regulated, the high-order mode becomes weaker, and the light spot becomes smaller. Fig. 9 As shown, by observing the light spot output by the 850nm laser having the metasurface 121, it can be seen that the light spot does not have the output light spot of the above structure.

[0090] Refer to the attached Fig.10 The comparison chart of the intensity distribution of the output light spot shows the laser output without the present metasurface 121 (green) and the laser output with the present metasurface 121 (blue). In the figure, the horizontal axis is the spot size and the vertical axis is the intensity distribution of the spot. It can be clearly seen that after being regulated by the present metasurface 121, the output intensity of the spot is increased from 0.02 to 0.045, and the efficiency is 2.25 times that of before.

[0091] Based on the same inventive concept, a method for using a semiconductor laser 100 is also disclosed, wherein the semiconductor laser 100 includes the above-mentioned metasurface 121 .

[0092] For example, this metasurface can be used in the fields of plane lenses, holographic optics, autonomous driving, remote sensing, ultra-high resolution imaging, beam generation, polarization devices, etc.

[0093] For specific examples and descriptions of beneficial effects of the method described in this embodiment, reference may be made to the description of the semiconductor laser 100 described above, which will not be repeated here.

[0094] Obviously, various changes and modifications may be made to the present invention by those skilled in the art without departing from the spirit and scope of the present invention. The present disclosure is not limited to the precise structure described above and shown in the accompanying drawings, and various changes and modifications may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims. Thus, if these changes and modifications of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these changes and modifications.

Claims

1. A metasurface unit, used for the light output port of a semiconductor laser, characterized in that: The metasurface unit comprises: a first column and a second column, wherein the first column and the second column are arranged sequentially from bottom to top; Wherein, the first column is a rectangular photonic crystal column, and the rectangular photonic crystal column is used to suppress radial and angular high-order modes of the output light; The tubular column is used to further control the light beam of the output light, thereby improving the single-mode output efficiency of the output light.

2. The metasurface unit according to claim 1, characterized in that: The side length of the cross section of the first column is controlled to be 0.15-0.35um, and the height is controlled to be 0.15-0.3um; the outer diameter of the second column is controlled to be 0.05-0.2um, and the inner diameter is controlled to be 0.04-0.1um.

3. The metasurface unit according to claim 1 or 2, characterized in that: The first column and the second column are made of at least one of Si3N4 and TiO2.

4. A semiconductor laser, characterized in that: include: Semiconductor laser light emitting structure with vertical cavity surface emitting laser structure ； The metasurface unit according to claims 1-3, wherein the metasurface unit array forms a metasurface, the metasurface is arranged at the light output port of the semiconductor laser light-emitting structure, and a coupling layer is arranged between the metasurface unit array and the semiconductor laser light-emitting structure; The metasurface unit array is a uniform annular array structure extending from the center of the light output port to the edge, and an array structure of n metasurface units is formed around any metasurface unit as the center.

5. The semiconductor laser according to claim 4, characterized in that The array structure is configured such that the distance between each array ring in the annular array gradually increases from the center of the light output port to the edge.

6. The semiconductor laser according to claim 4, characterized in that The first column of the metasurface unit is a rectangular photonic crystal column, and the rectangular photonic crystal column is used to rotate clockwise to radially control the output light.

7. The semiconductor laser according to claim 4, characterized in that The coupling layer is a SiO2 layer, and the thickness of the SiO2 layer is controlled to be 15-25 nm.

8. The semiconductor laser according to claim 4, characterized in that In the metasurface unit array, the second column is configured to have a structure in which the diameter gradually decreases from the center of the light output port toward the outside.

9. A method for preparing a semiconductor laser, characterized in that the steps include: A coupling layer is plated on the semiconductor laser light emitting structure by a magnetron sputtering process; A mask layer is printed on the upper side of the coupling layer, wherein the mask layer is provided with a first column pattern corresponding to the light output port, and then a filling column is plated inside the first column pattern to obtain a column layer; cleaning the mask layer on the pillar layer using a solvent, thereby leaving the filled pillars; The upper part of the filling column is etched out into a second column by an etching process to obtain a semiconductor laser with a super surface.

10. The method for preparing a semiconductor laser according to claim 9, characterized in that: After the coupling layer is plated on the semiconductor laser light-emitting structure, the photoresist is printed on the coupling layer through a two-photon polymerization process, thereby obtaining the mask layer on the coupling layer. The mask layer is provided with a first column pattern at a position corresponding to the light output port, and the first column pattern is a rectangular pattern.

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