Grating structure for vertical cavity surface emitting laser and laser

Abstract

The invention provides a grating structure for a vertical cavity surface emitting laser and the laser, and relates to the technical field of lasers, the grating structure is integrated on the surface of an upper distributed Bragg reflector and comprises an elliptical central area and periodic stripes radially distributed around the elliptical central area, and the stripe period is gradually changed along the radial direction. According to the structure, the laser polarization direction is locked through geometric anisotropy of long and short axes of an ellipse, and a high-order transverse mode is effectively inhibited through differential diffraction loss of stripes to an edge light field; meanwhile, the center size of the ellipse is matched with the light field distribution range of the active area, so that efficient feedback of a fundamental mode is ensured. While the output power of the device is ensured, the problems of unstable polarization and multi-transverse-mode lasing of a conventional device are solved, stable output of high light beam quality is realized, and the device is suitable for precise scenes such as optical communication and 3D sensing.

Description

Technical Field

[0001] This application relates to the field of laser technology, and more specifically, to a grating structure for a vertical cavity surface-emitting laser and a laser. Background Technology

[0002] Vertical-cavity surface-emitting lasers (VCSELs) have been widely used in short-distance optical interconnects, 3D sensing, Time-of-Flight (ToF) ranging, face recognition, and lidar due to their advantages such as low threshold current, high modulation rate, small divergence angle, and ease of integration into two-dimensional arrays. However, the resonant cavity structure of conventional VCSELs is typically approximately cylindrically symmetrical, with weak anisotropy in the active region and distributed Bragg mirrors (DBRs). This results in the laser polarization direction being highly sensitive to operating temperature, injection current, and stress disturbances, easily exhibiting random jumps between two orthogonal crystal orientations and significant polarization instability. Regarding transverse mode characteristics, using a larger transverse dimension of the active region or a larger oxide aperture to increase output power can easily excite multiple higher-order transverse modes within the resonant cavity. This leads to a multi-peak or ring-shaped distribution of the far-field beam, increased divergence angle, and decreased beam quality, making it difficult to meet the requirements of polarization stability and single-transverse mode output for applications such as polarization-sensitive optical communication, nonlinear frequency conversion, and high-precision 3D imaging.

[0003] In existing technologies, it has been proposed to introduce bar gratings, slotted structures, or photonic crystal structures on the VCSEL surface to improve polarization and transverse mode characteristics, or to achieve mode selection and polarization control by adjusting parameters such as oxide aperture and stress layer. However, bar gratings have a single polarization selection direction and limited suppression of transverse modes; reducing the oxide aperture will significantly reduce output power and aggravate thermal effects; complex photonic crystal structures are highly dependent on process precision, making it difficult to balance cost and mass production consistency.

[0004] Meanwhile, for applications combining VCSEL arrays with diffractive optical elements and microlens arrays, existing array beam shaping methods often approximate the unit spot as an isotropic Gaussian distribution, neglecting the elliptical anisotropic characteristics introduced by the cavity structure and surface microstructure. This makes it difficult to coordinately optimize illumination distribution, polarization distribution, and beam quality at the array scale. Therefore, how to achieve joint constraints on polarization and transverse modes through surface structures with geometric anisotropic characteristics while being compatible with existing VCSEL manufacturing processes, and how to utilize this anisotropic characteristic at the array level for algorithm-driven beam shaping and illumination uniformity optimization, still requires further research. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a grating structure and a laser for a vertical cavity surface-emitting laser.

[0006] In a first aspect, this application provides a grating structure for a vertical-cavity surface-emitting laser, comprising: The central region is elliptical in shape, having mutually perpendicular major and minor axes, wherein the length of the major axis is greater than the length of the minor axis; and The radial stripe region is composed of multiple stripe structures distributed around the periphery of the central region; The plurality of stripe structures extend radially outward along the central region and are arranged periodically in the circumferential direction; The central region and the radial stripe region together define a structural distribution with geometric anisotropy.

[0007] Optionally, the ratio of the major axis length to the minor axis length of the central region is 1.2:1 to 5:1; The plurality of stripe structures are symmetrically distributed along the long axis and the short axis.

[0008] Optionally, the period of the radiating stripe region is distributed in a non-linear gradient along the radial direction, and the period of the stripe structure gradually increases or decreases from the outer periphery of the central region outward.

[0009] Optionally, the ratio of the width of the stripe structure to the gap width between adjacent stripe structures is 0.3:1 to 0.8:1.

[0010] Secondly, please provide a vertical-cavity surface-emitting laser, including: A substrate, a lower distributed Bragg reflector, an active region, and an upper distributed Bragg reflector are stacked together; and A grating structure integrated into the light-emitting side surface of the upper distributed Bragg mirror; The grating structure is the grating structure described in the first aspect above, and the central region of the grating structure is arranged corresponding to the center of the active region.

[0011] Optionally, the upper distributed Bragg mirror includes alternating layers of a first refractive index material and a second refractive index material. The grating structure is formed in the topmost material layer of the upper distributed Bragg mirror, and the grating structure and the upper distributed Bragg mirror are integrally formed.

[0012] Optionally, the vertical cavity surface-emitting laser further includes an oxide confinement layer located between the upper distributed Bragg mirror and the active region, the oxide confinement layer having oxide holes for confining the current injection path; The center of the oxide hole is concentrically aligned with the central region of the grating structure, and the central region of the grating structure completely covers the projection area of ​​the oxide hole in the light emission direction.

[0013] Optionally, the grating structure includes multiple etching grooves, the depth of which is less than the thickness of the topmost material layer of the upper distributed Bragg mirror, so that the topmost material layer retains a continuous material layer of a predetermined thickness at the bottom of the etching groove.

[0014] Thirdly, this application provides a beam shaping method for a vertical-cavity surface-emitting laser array, the array comprising a plurality of vertical-cavity surface-emitting lasers as described in the second aspect above, the method comprising: The far-field light intensity distribution data of the array is collected on a preset projection plane; In a coordinate system with the major and minor axes of the elliptical spot of each vertical cavity laser as the main directions, a two-dimensional elliptical anisotropic multi-scale transformation is performed on the far-field intensity distribution data to obtain an elliptical anisotropic coefficient matrix. The wavelet basis function of the multi-scale transformation has different scale parameters in the direction corresponding to the major axis and the direction corresponding to the minor axis. Based on the elliptic anisotropy coefficient matrix, the coefficients in each scale sub-band are divided according to the position of the vertical cavity surface-emitting laser in the array to obtain the elliptic anisotropy eigenvector corresponding to each vertical cavity surface-emitting laser. Based on the preset target illumination distribution and / or target polarization distribution, construct the target elliptic anisotropic eigenvector, and use the driving intensity of each vertical cavity surface laser as the optimization variable to establish an optimization model with elliptic anisotropic eigenvalue constraints and sparse constraints. Solve the optimization model to obtain the driving intensity solution vector corresponding to each vertical cavity surface emitter (VCSEL), and control the switching state, driving current and / or driving duty cycle of each VCSEL in the array according to the driving intensity solution vector.

[0015] Optionally, performing a two-dimensional elliptic anisotropic multi-scale transformation on the far-field light intensity distribution data to obtain the elliptic anisotropic coefficient matrix includes: Based on the geometric arrangement of each vertical cavity surface-emitting laser in the array, determine the center position of the reference spot on the preset projection plane for each emitting unit; Construct a set of elliptical window functions centered on the center positions of each reference spot; The far-field light intensity distribution data is weighted with each elliptical window function and a local two-dimensional elliptical anisotropic multi-scale transformation is performed in the corresponding local coordinate system to obtain the local elliptical anisotropic coefficient submatrix assigned to the corresponding emission unit. The local elliptical anisotropic coefficient submatrices are then concatenated according to the array index dimension to form the elliptical anisotropic coefficient matrix.

[0016] Compared with existing technologies, this application introduces a geometrically anisotropic grating structure on the light-emitting side, consisting of an elliptical central region and a periodically radiating stripe region surrounding it. This allows the resonant cavity to achieve a clearly distinguishable structural distribution in the long and short axis directions. On the one hand, the elliptical central region establishes two orthogonal principal axes, which, together with the stripe structure extending radially and arranged periodically in the circumferential direction, breaks the cylindrical symmetry of conventional VCSELs. This introduces differentiated radiation losses and feedback conditions for the two orthogonal polarization modes, which is beneficial for achieving selective stability of polarization direction without changing the active region material system. On the other hand, the radiating stripe region simultaneously forms additional spatial modulation of the transverse electromagnetic field distribution in both the radial and angular directions. Compared with structures that only add stripes in a single direction, this is more conducive to suppressing outwardly expanding higher-order transverse modes and enhancing the constraint of the fundamental mode in the elliptical central region. Thus, while being compatible with traditional DBR epitaxy and planar processes, it achieves synergistic optimization of polarization control and transverse mode control with a simpler surface pattern, improving the polarization stability and beam quality of the VCSEL, while maintaining good process feasibility and array integration adaptability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the planar structure of the elliptical wheel-shaped grating in an embodiment of this application; Figure 2 This is a schematic diagram of the longitudinal cross-sectional structure of a vertical cavity surface-emitting laser using an elliptical wheel-shaped grating in an embodiment of this application; Figure 3 This is a flowchart illustrating a method for obtaining an elliptic anisotropy coefficient matrix, provided in an embodiment of this application. Detailed Implementation

[0018] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0019] In a specific embodiment, the grating structure for a vertical-cavity surface-emitting laser (VCSEL) of this application is preferably formed on a planar material layer near the light-emitting side of the VCSEL. This planar material layer can be one layer in a semiconductor distributed Bragg mirror layer, or it can be a dielectric functional layer covering the surface of the mirror. The specific material and layer structure can be selected according to the target operating wavelength, process platform, and device packaging method. In an exemplary embodiment, the entire grating structure is located within an approximately flat light-emitting surface region, and its outline is defined in the plane as including two parts: a central region and a radiating stripe region surrounding the central region.

[0020] The central region has an elliptical outline in the plane. The outline of the ellipse can be a strictly geometric elliptical curve, or an approximate elliptical closed curve fitted according to the shape of the target light spot during layout design, such as a smooth closed outline with rounded corners or small broken line segments. In this embodiment, for ease of explanation, the elliptical central region has a major axis and a minor axis relative to a preset reference coordinate system. The major axis and minor axis are geometrically perpendicular to each other, and the dimension in the direction of the major axis is significantly elongated relative to the dimension in the direction of the minor axis, so as to form a pair of orthogonal principal directions in the plane. The interior of the central region can be a continuous solid area of ​​material, or a small number of auxiliary openings or alignment marks can be arranged according to process requirements, but no periodic stripe structure spreading circumferentially is set, thereby forming a clearly defined "grating central region" visually and geometrically.

[0021] A radial stripe region is formed around the outer periphery of the aforementioned elliptical central region. This radial stripe region is defined in the plane as one or more annular areas extending outward from the boundary of the central region. This radial stripe region consists of multiple stripe structures, each extending approximately radially outward from the central region in the plane. Its inner end is adjacent to the outer contour line of the central region, and its outer end extends away from the central region. In specific implementations, the stripe structures can be formed by local etching to create strip-shaped grooves, or by selective growth or deposition to create strip-shaped protrusions. A combination of grooves and protrusions can also be used, as long as they appear strip-shaped in the plane projection and their geometric extension direction is substantially consistent with the radial direction.

[0022] In the circumferential direction, the stripe structures are arranged sequentially around the outer periphery of the elliptical central region at predetermined angular intervals. The included angle between the centers of adjacent stripes can be designed to be substantially equal to form a periodic array in the circumferential direction. In some embodiments, periodic perturbations or local defects can be introduced by appropriately adjusting the stripe intervals in local areas, thereby fine-tuning the radiation characteristics of a specific transverse pattern. Overall, when viewed along the circumferential direction with the geometric center of the central region as the pole, the stripe structure can be seen to present a "wheel spoke" arrangement of concentric rings pointing radially towards the center, with certain gaps between the stripes. The stripes and gaps together in the plane constitute a grating pattern with a certain opening fill factor distribution.

[0023] Since the geometric dimensions of the central region are different in the major and minor axis directions, and the radial stripe area expands around the periphery of the central region, when cross-sections passing through the geometric center are taken along the major and minor axis directions of the ellipse, two sets of stripe distributions with significantly different stripe coverage width, number of stripes, stripe density, and opening fill factor can be obtained.

[0024] For example, along the major axis, the central region extends longer, resulting in a narrower effective width of the radiating fringe regions on both sides and a smaller number of usable fringes. Conversely, along the minor axis, the central region extends shorter, leading to a larger radiating fringe region on both sides and a denser fringe arrangement. It is through this synergistic arrangement between the elliptical central region and the fringe structure extending radially around its periphery and arranged periodically in the circumferential direction that the grating structure of this embodiment exhibits significantly different geometric distribution characteristics along the two orthogonal principal axes, thereby forming a grating structure with geometric anisotropy in the plane. This geometric anisotropy does not depend on a specific material system or specific process parameters, and is applicable to vertical-cavity surface-emitting lasers with different operating wavelengths, active region sizes, and packaging forms. Only the ellipse size, number of fringes, fringe spacing, and fringe extension range need to be adapted and adjusted during the layout design stage in conjunction with the optical and electrical specifications of the target device.

[0025] Based on the aforementioned grating structure for vertical-cavity surface-emitting lasers (VCSELs), to achieve a more balanced overall performance between polarization selectivity, transverse mode suppression capability, and fabrication feasibility, in a preferred embodiment, the major axis and minor axis of the elliptical central region are set to an unequal ratio, and the major and minor axes remain perpendicular to each other. Specifically, the geometric dimension of the central region along the major axis is larger than that along the minor axis, and the ratio of its major axis to minor axis can be designed within a preset range, for example, between 1.2:1 and 5:1, so as to avoid the ellipse being too "slender" or too close to a circle while breaking the circular symmetry. In actual design, different major-to-minor axis ratios can be scanned and optimized using optical simulation tools (such as software based on finite-difference time-domain or frequency-domain coupled-wave analysis) according to the target operating wavelength, the required ellipticity of the far-field spot, and the target polarization extinction ratio, and one or more typical values ​​suitable for specific applications can be selected, such as 1.5:1, 2:1, or 3:1. Those skilled in the art will understand that, provided the basic relationship that the major axis is greater than the minor axis is satisfied, the ratio of the major axis to the minor axis can be finely adjusted according to subsequent process capabilities and device packaging space, and is not limited to the specific values ​​mentioned above.

[0026] To fully utilize the two principal axes introduced by the elliptical central region, in another preferred embodiment, the arrangement of the multiple stripe structures surrounding the central region in the plane can be configured as a symmetrical arrangement about the major and minor axes. Specifically, with the center of the ellipse as the center of symmetry, a symmetry axis is drawn along the major axis, and the geometric shape, quantity, and spacing of the stripe structures on both sides of this symmetry axis can be designed as mirror images. Similarly, with the minor axis as the other symmetry axis, the stripe structures on both sides of this direction can also be designed as mirror images. Through this dual-axis symmetrical arrangement, the grating as a whole can exhibit paired symmetrical geometric features in two orthogonal directions, which is beneficial for forming stable polarization selectivity and mode selectivity in these two directions respectively.

[0027] In the actual layout implementation process, the symmetry relationship allows for small deviations introduced by lithography and etching tolerances. As long as the overall trend of symmetry is maintained in the directions of the major and minor axes, optical effects similar to those of a strictly symmetrical structure can be obtained.

[0028] Based on the above structure, in order to further control the grating coupling strength at different radial positions and the selectivity for different transverse modes, in an exemplary embodiment, the radial fringe region surrounding the elliptical center region can be designed as a structure in which the fringe period is gradually distributed radially. Specifically, starting from a ring of fringe near the outer periphery of the central region, it extends outward ring by ring or continuously, and the radial spacing between the fringe centers can gradually increase or decrease according to a preset nonlinear variation law.

[0029] For example, in the inner region near the center, a smaller fringe period can be used to enhance the modulation of the field distribution near the center of the spot; in the outer region, the fringe period is gradually increased, allowing higher-order transverse modes to experience different coupling conditions as they expand outward, thus creating differentiated selection of different modes within the cavity. The term "nonlinear gradient" refers to the fact that the fringe period does not simply increase or decrease linearly with a fixed step size with radial position, but can be achieved through segmented settings, gradual adjustments, or a variation curve set based on simulation results. For example, a smaller variation can be used in the section near the center, and a larger variation in the outer regions, to more precisely match the field distribution of the target mode. The specific radial fringe period sequence can be determined through optical simulation and process feasibility assessment; this invention does not limit the specific mathematical form.

[0030] In another embodiment, to balance the diffraction efficiency of the grating and the manufacturing window, the ratio between the linewidth of each fringe structure in the radiating fringe region and the gap width between adjacent fringes can be set within a suitable range. Taking a set of fringes and gaps at the same radial position as an example, the ratio of the width of the fringe under circumferential projection to the circumferential gap width between adjacent fringes can preferably be designed to be 0.3:1 to 0.8:1, so that the opening fill factor is neither too low, resulting in insufficient coupling strength, nor too high, causing insufficient process resolution or etching residue.

[0031] In practice, the fringe width and gap width can be kept approximately constant radially, or they can be adjusted synergistically in conjunction with the aforementioned fringe periodic gradient characteristics. For example, a relatively large fill factor can be used in the inner region to enhance local modulation, while a slightly smaller fill factor can be used in the outer region to reduce overall erosion of the epitaxial layer surface. The specific values ​​of the fringe width and gap width can be selected based on the lithographic resolution, etching anisotropy, and target operating wavelength. Different combinations of the above ratio ranges can achieve the function of the geometrically anisotropic grating structure described in this invention, and are not limited to a fixed size combination.

[0032] In a specific embodiment of the present invention, the vertical-cavity surface-emitting laser can adopt a typical top-emitting structure, which includes a substrate, a lower distributed Bragg reflector (lower DBR), an active region, and an upper distributed Bragg reflector (upper DBR) stacked sequentially. The substrate can be a gallium arsenide substrate, an indium phosphide substrate, or other single-crystal substrate material suitable for the target emission wavelength. The substrate type can be n-type or p-type conductivity type depending on the target application and is not limited. The lower DBR can be composed of two semiconductor or dielectric materials with different refractive indices stacked alternately to provide the high reflectivity feedback required in the vertical cavity. The active region can adopt multiple quantum wells, active multiple quantum well stacks, or other gain structures, and is disposed between the upper and lower DBRs and achieves carrier injection through electrodes. The upper DBR is also composed of multiple periodic alternating layers of refractive indices, and a material layer of sufficient thickness is reserved on its emission side to integrate a surface grating structure. For VCSELs operating in the near-infrared or short-wave infrared bands, the material combination of the active region and the DBR can be selected according to existing mature process platforms, such as GaAs / AlGaAs system, InP-based system, etc. This invention does not limit the specific material system.

[0033] To achieve modulation of the intracavity light field without adding additional heterogeneous interfaces and complex packaging structures, the grating structure described in this embodiment is preferably directly integrated onto the light-emitting side surface of the upper DBR. That is, on the side where the device ultimately emits light, the aforementioned elliptical central region and radiating stripe region are formed on the surface of the upper DBR or a functional layer near the surface through photolithography and etching processes. Specifically, after the epitaxial growth of the upper DBR is completed, one or more rounds of photolithography can be performed at the wafer level according to the device layout to transfer the outline of the elliptical central region and the stripe structure surrounding the central region into the photoresist pattern. Subsequently, the pattern is etched to a predetermined depth through dry etching or wet etching, thereby obtaining the desired planar grating morphology on the light-emitting side of the upper DBR.

[0034] In some implementations, the grating structure can also be formed on a transparent dielectric film covering the DBR, such as a silicon dioxide film or a silicon nitride film, in order to introduce additional phase modulation or surface protection functions while maintaining the reflective properties of the DBR.

[0035] In this embodiment, the central region of the grating structure is preferably positioned corresponding to the geometric center of the active region. Specifically, in the direction perpendicular to the substrate, the geometric center of the elliptical central region substantially coincides with the geometric center of the lower active region in the plane, meaning that when the effective light-emitting area of ​​the active region is projected onto the upper DBR light-emitting surface, the projected area falls within the range of the elliptical central region.

[0036] To achieve this correspondence, alignment marks or process layer marks in the epitaxial structure can be used during layout design and mask alignment to uniformly arrange and align the grating pattern with the active region current injection holes or active region growth windows. This ensures that the center deviation between the central region and the active region at the chip scale is controlled within a predetermined tolerance, such as within the micrometer or even submicrometer range. This corresponding arrangement concentrates the energy of the intracavity master mode primarily at the longitudinal position corresponding to the elliptical center region. This facilitates the subsequent generation of differentiated radiation losses and feedback conditions for different transverse and polarization modes through the radiation stripe region, thereby achieving polarization control and transverse mode control at the device structure level that adapts to the natural mode distribution of the active region.

[0037] It should be noted that the aforementioned vertical-cavity surface-emitting lasers can operate independently as a single emitting unit, or they can be arranged in a one-dimensional or two-dimensional array on the same substrate and used in combination with external diffractive optical elements, microlens arrays, or other optical systems. In array applications, the grating structure of each emitting unit can adopt the same or slightly different central region size and fringe arrangement parameters to adapt to different divergence angles, beam shapes, or local illumination requirements. The basic relationship that the central region corresponds to the center of each active region can remain unchanged in the array design, thereby ensuring good consistency in the mode and polarization characteristics of the output beam of each emitting unit at the device level.

[0038] Based on the aforementioned vertical cavity surface-emitting laser, in a preferred embodiment, the upper distributed Bragg mirror adopts a structure in which two material layers with different refractive indices are stacked alternately.

[0039] Specifically, multiple periods can be formed by alternately stacking a first refractive index material layer and a second refractive index material layer to provide high reflectivity feedback at the target operating wavelength. The first refractive index material layer and the second refractive index material layer can be aluminum gallium arsenide of different compositions, gallium arsenide and aluminum gallium arsenide, or other semiconductor or dielectric materials with different refractive indices. This invention does not limit the specific material combination.

[0040] To facilitate fabrication, the top layer of the upper DBR can be made of a material compatible with the underlying layer pair. After epitaxial growth, the aforementioned grating structure, including the elliptical central region and radiating stripe region, is directly formed within this top layer through photolithography and etching. In other words, the grating structure is obtained through local patterning within the top layer of the upper DBR, rather than by depositing a separate grating film layer. This ensures the grating structure and the upper DBR are integrally formed in terms of both material and structure, reducing interface reflection discontinuities, simplifying the process flow, and improving device reliability under temperature cycling and packaging stress. In actual fabrication, by controlling the etching formula and etching time, the trenches or protrusions of the grating can be strictly confined within the top layer material, preventing them from intruding into the underlying layer pair, thus ensuring the overall reflectivity of the DBR remains within the design range.

[0041] In another preferred embodiment, the vertical-cavity surface-emitting laser (VCSEL) further includes an oxide confinement layer disposed between the upper distributed Bragg mirror (DBR) and the active region. This layer defines the current injection path and works in conjunction with the grating structure to shape the lateral optical mode. The oxide confinement layer can be an aluminum-rich semiconductor layer, such as a high-aluminum-content aluminum gallium arsenide layer. During device fabrication, it forms an oxide region laterally through wet or vapor oxidation. The remaining unoxidized region constitutes the effective aperture through which the current and optical field mainly pass, i.e., the oxide aperture. In this embodiment, the geometric center of the oxide aperture in the plane is preferably concentrically aligned with the elliptical center region of the grating structure, meaning that their centers in the chip plane essentially coincide. To achieve this concentricity, the position, thickness, and aperture size of the oxide confinement layer can be matched with the thickness of the upper DBR top layer during the epitaxial design stage. During the layout design stage, the current injection electrodes, oxide windows, and grating patterns can be uniformly arranged, and multi-layer alignment marks can be used to ensure the central consistency between each process step.

[0042] The planar shape of the oxide aperture can be near-circular, elliptical, or other shapes suitable for carrier and light field distribution, as long as its projected area in the light-emitting direction can be completely covered by the elliptical central region of the grating structure. The advantage of this arrangement is that the energy concentration region of the main optical modes in the cavity is aligned with the region of strongest geometric anisotropy of the grating. This allows for preliminary constraint of the current and refractive index distribution of higher-order transverse modes using the oxide aperture, and also enables fine selection of the remaining modes and polarization on the light-emitting side using the grating, achieving a synergistic effect of current constraint and grating modulation.

[0043] In another embodiment, in order to introduce sufficient surface modulation depth while maintaining the overall mechanical strength and reflective performance of the upper distributed Bragg mirror, the grating structure is preferably implemented in the form of an etched groove, and its etching depth is controlled within the thickness of the top layer of the upper DBR material.

[0044] Specifically, after the grating pattern is transferred to the top layer material, the top layer material is etched in a controlled manner by dry etching, wet etching, or a combination of both, forming multiple etching grooves in the stripe area. At the bottom of the etching groove, a continuous material layer is retained at the interface between the upper DBR and the next layer, which is a residual layer of a preset thickness.

[0045] The thickness of the residual continuous layer can be determined by comprehensively considering the target operating wavelength, the refractive index of the top layer material, and the desired phase modulation depth. Generally, it can be selected as a part of the top layer thickness, so that the grating can locally change the effective refractive index and interface morphology of the light-emitting side without completely etching through the top layer and exposing the underlying layer pair, thus avoiding the introduction of additional scattering loss or weakening the reflectivity of the DBR.

[0046] In practical processes, etching depth can be calibrated and controlled through methods such as etching endpoint monitoring, sample calibration, or step-by-step etching testing. This ensures the uniformity of etching trench depth and the consistency of residual layer thickness in different stripe regions. The grating structure formed in this way remains a macroscopically integrated structure with the upper DBR, while microscopically, optical field modulation is achieved through local etching within the top layer. This improves the device's polarization stability and transverse mode control capability without adding additional interfaces.

[0047] In one specific embodiment of the present invention, a vertical-cavity surface-emitting laser array can be arranged on a printed circuit board or a package substrate to form a one-dimensional or two-dimensional array structure for providing an illumination source for 3D structured light, face recognition, or Time-of-Flight (ToF) ranging systems. The output beams of each emitting unit can be superimposed and projected onto a preset projection plane using collimating optical elements, diffractive optical elements, or a microlens array. This projection plane can be a calibration screen, the surface of a diffuse reflector, or an imaging plane located at the target working distance.

[0048] The system is equipped with an imaging detector, such as an industrial camera or image sensor module, arranged corresponding to the projection plane to acquire far-field light intensity distribution images formed by the array illumination. During calibration or operation, the control module illuminates one or more vertical cavity surface-emitting lasers in the array according to a preset method, acquires light intensity distribution data containing the far-field light spots of each emitting unit through the imaging detector, and transmits it to the data processing unit.

[0049] In this embodiment, the data processing unit is preferably a processor or dedicated accelerator with matrix operation capabilities, such as a microprocessor or digital signal processor equipped with a floating-point unit, or an embedded computing platform configured with a graphics processing unit or a field-programmable gate array. The data processing unit first establishes a principal direction coordinate system for the imaging plane based on the array layout, optical system parameters, and the spot positions measured during the calibration phase, corresponding to the major and minor axes of the elliptical spots of each vertical cavity surface-emitting laser.

[0050] In simple cases, a set of fixed principal axis directions can be directly established in the image coordinate system using the chip assembly direction and the major axis direction of the ellipse defined in the device design. When higher precision is required, the principal axis directions of each spot can be estimated in a local area by analyzing the second moment of the spot, the structure tensor, etc., and the local coordinate system can be fine-tuned accordingly.

[0051] Subsequently, the data processing unit performs a two-dimensional elliptic anisotropic multi-scale transformation on the far-field light intensity distribution data in the aforementioned principal direction coordinate system.

[0052] Specifically, a set of two-dimensional filter kernels supported by ellipses in the plane can be constructed. These filter kernels have a larger spatial scale in the direction corresponding to the major axis of the elliptical spot and a smaller spatial scale in the direction corresponding to the minor axis, thus exhibiting different resolution capabilities for light intensity distribution in different directions. By performing convolution or equivalent linear transformation on the far-field light intensity data at multiple scale levels and multiple directional sub-bands, a set of elliptical anisotropy coefficient matrices can be obtained. Each channel of the matrix reflects the local energy and structural characteristics of the light intensity distribution at different spatial scales and in different principal directions.

[0053] Such multi-scale transformations can be implemented on general-purpose processors using software libraries, or hardware-accelerated on graphics processing units or programmable logic devices to meet the real-time processing requirements of high-resolution imaging and large-scale arrays.

[0054] After obtaining the elliptic anisotropy coefficient matrix, the data processing unit combines the spatial geometric arrangement information of each vertical cavity surface-emitting laser in the array to divide the coefficients in each scale subband according to the position of the emitting unit in the array.

[0055] For example, based on the geometric mapping relationship of the array on the projection plane, one or more corresponding image regions or weight masks can be defined for each emission unit. Elliptic anisotropy coefficients in sub-bands at different scales and directions within these regions can be extracted and combined into a feature vector for the emission unit according to a preset rule. This feature vector may include energy distribution along the major axis and along the minor axis at multiple scales, relative intensity of the main lobe and side lobes, statistics related to the ellipticity of the spot, etc., thereby compactly characterizing the elliptic anisotropy far-field characteristics of each emission unit in the transform domain.

[0056] To achieve the desired illuminance and / or polarization distribution of the array in the target application scenario, the data processing unit constructs the corresponding target elliptic anisotropic eigenvector based on system design requirements or upper-layer application instructions. This target eigenvector can be derived from simulation results of an ideal illumination model or from the summarization and interpolation of experimental measurement results for several preferred configurations. Then, using the driving intensity (e.g., driving current amplitude, duty cycle, or gray level) of each vertical-cavity surface-emitting laser as the optimization variable, an optimization model with elliptic anisotropic eigenvector constraints and sparsity constraints is established: on the one hand, the elliptic anisotropic eigenvector generated by the current driving intensity combination is constrained to be as close as possible to the target eigenvector; on the other hand, the number of simultaneously lit emitting units or the overall driving power is limited by sparsity or regularization constraints to balance engineering indicators such as illuminance uniformity, system efficiency, and thermal management.

[0057] In the specific solution process, the data processing unit can use iterative optimization methods, convex optimization methods, or heuristic search methods, and select an appropriate solution strategy based on the array size and real-time requirements to obtain a set of drive intensity solution vectors corresponding to each transmitting unit.

[0058] After optimization, the control module configures the array drive circuit according to the solution vector, sets the switching state, drive current magnitude and / or duty cycle of each channel, so that the array forms a light field that approximates the target illuminance distribution and / or target polarization distribution when it actually illuminates the target space.

[0059] The beam shaping process described above can be performed once during the calibration stage before the product leaves the factory to generate a fixed drive configuration table, or it can be triggered periodically or on demand during product operation to compensate for deviations caused by environmental changes, device aging, or mechanical offset, thereby maintaining relatively stable illumination uniformity and beam quality throughout the entire life cycle.

[0060] Optional, see Figure 3 The flowchart of a method for obtaining an elliptic anisotropy coefficient matrix provided in this application embodiment includes steps S101~S104, wherein: S101: Determine the center position of the reference spot on the preset projection plane for each emitting unit based on the geometric arrangement of the vertical cavity surface-emitting lasers in the array; S102: Construct a set of elliptical window functions with the center position of each reference spot as the center; S103: The far-field light intensity distribution data is weighted with each elliptical window function and a local two-dimensional elliptical anisotropic multi-scale transformation is performed in the corresponding local coordinate system to obtain the local elliptical anisotropic coefficient submatrix allocated to the corresponding emission unit. S104: And the local elliptical anisotropic coefficient submatrices are concatenated according to the array index dimension to form the elliptical anisotropic coefficient matrix.

[0061] In step S101, the reference spot center position of each emitting unit on the preset projection plane is determined according to the geometric arrangement of each vertical cavity surface emitting laser in the array.

[0062] Specifically, the coordinates of each transmitting unit in the array layout, the geometric parameters of the projection optics system, and the calibration images obtained during factory calibration can be used to establish a mapping relationship from array index to image coordinates on the projection plane.

[0063] In a simple implementation, the theoretical spot center position can be calculated directly based on the array arrangement and the magnification of the collimating optics. In applications requiring higher precision, one or a few emitting units can be lit sequentially during the calibration phase, and the spot center can be extracted from the measured far-field image using image processing methods (such as centroid-based, peak search, or template matching positioning algorithms), and the measured position can be used as the reference spot center position for the corresponding emitting unit.

[0064] In step S102, a set of elliptical window functions is constructed with the center positions of each reference spot as the center. The elliptical window function can be understood as a two-dimensional weighted distribution used for local weighting on the far-field light intensity distribution data. This weight has a larger value near the center of the reference spot, gradually decreases outwards, and approaches zero in regions far from the spot, thus spatially partitioning the spot contributions of different emitting units. Each elliptical window function preferably has an elliptical support region in the plane that approximately matches the major and minor axes of the corresponding elliptical spot of the emitting unit. Its major axis direction is consistent with the main divergence direction of the spot, and the dimensions of the major and minor axes can be set according to the expected spot size, array spacing, and spot overlap.

[0065] For example, when the spacing between emission units is large and the light spot overlap is small, the elliptical window can be designed to be relatively compact; while in arrays with significant light spot overlap, the size of the elliptical window can be appropriately enlarged to cover a sufficient energy area, and the robustness of subsequent feature extraction can be improved by the overlap between windows.

[0066] The specific weighting function of the elliptical window can take the form of a flat top with transition edges, a Gaussian-like distribution, or other smooth window forms. This invention does not limit the specific mathematical expression.

[0067] In step S103, the far-field light intensity distribution data is weighted with each elliptical window function, and a local two-dimensional elliptical anisotropic multi-scale transformation is performed in the corresponding local coordinate system to obtain the local elliptical anisotropic coefficient sub-matrix assigned to the corresponding emission unit. Specifically, for each emission unit, the data processing unit can extract a local region on the image using the center position of its reference spot, and multiply this local region with the corresponding elliptical window function point by point to highlight the spot contribution of this unit and suppress interference from neighboring units. Based on this, a local coordinate system is defined with the center of the reference spot as the origin, according to the major and minor axes of the elliptical spot of this unit. The weighted local light intensity data is projected into this local coordinate system, and then a two-dimensional elliptical anisotropic multi-scale transformation is performed in this local coordinate system.

[0068] The multi-scale transform wavelet basis used has different effective scale parameters in the long axis and short axis directions, which makes the resolution of far-field divergence and mode structure in the long axis direction different from that in the short axis direction, thus better matching the anisotropic spot shape introduced by the elliptical grating structure of the emission unit.

[0069] After transformation, a set of two-dimensional coefficient distributions for the local region can be obtained. These coefficients are then organized according to a predetermined scale and direction to form the local elliptic anisotropic coefficient submatrix corresponding to the emission unit.

[0070] In step S104, the local elliptic anisotropy coefficient submatrices obtained from each transmitting unit are spliced ​​together according to the array index dimension to form the overall elliptic anisotropy coefficient matrix.

[0071] Specifically, a fixed index position can be assigned to each emitter unit in the array. For example, according to row and column numbers or one-dimensional indices, its local coefficient submatrix can be attached to a predetermined sub-block position in the global matrix, so that the global matrix can correspond to the spatial arrangement of the array in the index dimension. The elliptic anisotropic coefficient matrix constructed in this way not only preserves the local anisotropic characteristics for individual emitter units, but also corresponds one-to-one with the array geometry in its overall structure. This is beneficial for subsequent extraction of feature vectors according to the emitter unit dimension, construction of optimization models, and solving for the driving strength of each unit.

[0072] It should be noted that the weighted window size, local area range, and submatrix stitching method described above can be adjusted according to the array size, optical system magnification, and processor resources. As long as the overall idea of ​​local transformation of the elliptical window centered on the transmitting unit + array-level coefficient stitching is followed, the coefficient matrix construction method described in this embodiment can be realized.

[0073] See Figure 1 This is a schematic diagram of the planar structure of the elliptical wheel-shaped grating in this embodiment of the application, including: the major axis a of the elliptical wheel-shaped grating region and the minor axis b of the elliptical wheel-shaped grating region.

[0074] See Figure 2 This is a schematic diagram of the longitudinal cross-sectional structure of a vertical cavity surface-emitting laser using an elliptical wheel-shaped grating in an embodiment of this application, including an elliptical wheel-shaped grating 1, an upper electrode 2, an upper distributed Bragg mirror (upper DBR) 3, an oxide confinement layer 4, an active region 5, a lower distributed Bragg mirror (lower DBR) 6, a substrate 7, and a lower electrode 8.

[0075] The technical solution of this application includes two parts: the design of an elliptical wheel-shaped grating structure and the design of a VCSEL device structure, as detailed below: Design for elliptical wheel-shaped grating structure: The elliptical wheel-shaped grating structure has an elliptical center area, with multiple sets of periodic stripes radiating outward from the center area to form a periodic structure similar to "wheel spokes". It also exhibits geometric anisotropy, meaning that the structural characteristics are different in the major axis direction and the minor axis direction.

[0076] The elliptical central region serves as the "core anchoring region" of the grating. The ratio of its major axis to its minor axis is designed based on the light field distribution characteristics of the active region of the VCSEL, ensuring that the light field generated by the active region can be effectively confined to the central region and reducing light field overflow at the edge. At the same time, the geometric anisotropy of the ellipse provides a structural basis for subsequent polarization selection, making it easier for polarized light in specific directions, such as the major axis direction, to match the grating structure.

[0077] For periodic radiation fringes, the fringes extend radially along the central elliptical region and are symmetrically arranged along the major and minor axes, ensuring uniform control of the light field in different directions. The period, width, and spacing of the fringes are designed according to the lasing wavelength of the VCSEL, so that the fringe period is adapted to the light wavelength (usually on the subwavelength or near-wavelength order). By utilizing the diffraction and interference effects of light, differentiated losses are generated for light with different polarization directions and different transverse modes. For polarized light along the major axis of an ellipse, its vibration direction is more compatible with the extension direction and periodic structure of the grating fringes, resulting in low diffraction loss. It can efficiently pass through the grating and be fed back to the VCSEL resonant cavity, satisfying the gain-loss balance condition for laser oscillation. For polarized light along the short axis or other non-target directions, the vibration direction has a low matching degree with the grating structure, the diffraction loss is large, and the oscillation condition cannot be met, so it is effectively suppressed. For high-order transverse mode light, its light field distribution diffuses towards the edge of the VCSEL, resulting in poor matching with the periodic fringes of the grating. Furthermore, the periodic design of the fringes in the edge region further increases its diffraction loss, causing the loss of high-order transverse mode to be much greater than its gain, making it unable to oscillate. Only the fundamental mode light (with its light field concentrated in the center, high matching with the grating, and low loss) can be output stably.

[0078] For VCSEL device structure design: The VCSEL employing this elliptical wheel-shaped grating structure includes, from bottom to top: Substrate: Select a substrate that matches the lattice of the semiconductor epitaxial layer (such as a GaAs substrate) to provide a growth basis for subsequent functional layers and ensure the stability of interlayer bonding; Lower Distributed Bragg Mirror (DBR): It is composed of two semiconductor materials with high and low refractive indices (such as AlAs and GaAs) stacked alternately, and is used to reflect the light generated in the active region and transmitted downward back to the resonant cavity, thereby improving the optical feedback efficiency. Active region: It adopts a multi-quantum-well structure, which is composed of alternating quantum well layers and barrier layers (such as InGaAs quantum well and GaAs barrier). It is the core region for laser generation. Its lateral size is adapted to the size of the elliptical central region of the elliptical wheel-shaped grating, ensuring that the light field can be efficiently controlled by the grating. Upper Distributed Bragg Mirror (Upper DBR): It is also composed of alternating layers of high and low refractive index semiconductor materials, forming a resonant cavity with the Lower DBR. Its top layer material is the same as the material of the elliptical wheel-shaped grating (e.g., both are GaAs), which facilitates the integration of the grating with the Upper DBR and reduces interface loss. Elliptical wheel-shaped grating structure: integrated on the top surface of the upper DBR, fabricated through photolithography and etching processes. Its elliptical central region is concentrically aligned with the active region and the center of the upper DBR to ensure the precision of light field control. Oxidation confinement layer (optional): disposed between the upper DBR and the active region, formed by selective oxidation process, its opening area is concentric with the elliptical center area of ​​the elliptical wheel-shaped grating, used to further confine the current injection range and light field distribution, and to work with the grating to enhance the transverse mode suppression effect. Electrodes (optional): including a lower electrode (fabricated on the bottom surface of the substrate) and an upper electrode (fabricated on the upper DBR surface or grating gap region), used for injecting current to drive the VCSEL to work.

[0079] In practical implementation, when the VCSEL is powered on, current is injected into the active region through the electrodes. Electron-hole pair recombination occurs in the quantum well of the active region, releasing photons and forming a light field. The light field propagates back and forth within the resonant cavity formed by the upper and lower DBRs, and is continuously amplified. When the light field propagates to the elliptical wheel-shaped grating at the top layer: Regarding polarization selection, polarized light along the major axis of the ellipse is fed back to the resonant cavity for further amplification due to its high matching degree with the grating structure and low loss. Polarized light in other directions is suppressed due to high loss, and finally outputs light with a fixed polarization direction. Regarding the selection of transverse modes, the fundamental mode light field is concentrated at the center, which has a high degree of matching with the grating and low loss, thus satisfying the oscillation condition; the higher-order transverse mode light field diffuses to the edge, which has a poor degree of matching with the grating and high loss, thus failing to oscillate, thereby achieving single transverse mode output; Ultimately, the VCSEL stably outputs a laser with a fixed polarization direction and a single transverse mode, exhibiting excellent beam quality.

[0080] The beneficial effects of this invention are mainly reflected in the following aspects: By using the geometric anisotropy and periodic design of the elliptical wheel-shaped grating, the output polarization direction is fixed (consistent with the major axis of the ellipse), achieving a high polarization suppression ratio and minimal influence of environmental factors such as temperature and current on the polarization direction, thus solving the polarization jump problem of conventional VCSELs; utilizing the differentiated loss design of the grating for higher-order transverse modes, higher-order transverse modes are effectively suppressed, with only the fundamental mode achieving stable output, resulting in a low beam quality factor (approaching the diffraction limit), meeting the requirements of high-precision applications; the elliptical wheel-shaped grating is fabricated using mature photolithography and etching processes, compatible with the epitaxial, oxidation, and electrode fabrication processes of conventional VCSELs, requiring no additional complex equipment and facilitating mass production; while achieving polarization stability and single-mode output, there is no need to excessively reduce the oxide aperture or sacrifice the active region area, ensuring the output power of the VCSEL and balancing performance and practicality; parameters such as the elliptical major axis / minor axis ratio and grating period can be adjusted according to different application scenarios (such as optical communication and 3D sensing) to adapt to VCSELs with different wavelengths and polarization requirements, making it widely applicable.

[0081] For example, the elliptical wheel-shaped grating and its integrated vertical cavity surface-emitting laser of the present invention can be fabricated in the following order. The following process steps are mainly used to illustrate the feasible implementation of the structure of the present invention. They are qualitative descriptions and do not limit specific numerical parameters or equipment models.

[0082] First, the design parameters of the elliptical wheel-shaped grating are determined. Based on the design lasing wavelength of the target VCSEL, the transverse dimension of the active region, and the expected polarization selectivity and transverse mode suppression requirements, the basic geometric parameters of the grating planar pattern are determined.

[0083] In this design, the ratio of the major axis to the minor axis of the elliptical central region can be set in conjunction with the target polarization extinction ratio to minimize radiation loss along the major axis, thus optimizing the target polarization direction. The fringe period of the radiation fringe region can be designed with reference to the operating wavelength and the effective refractive index on the emitting side to adapt to the diffraction coupling characteristics of the light. The ratio of fringe width to gap width can be selected based on polarization suppression and process resolution requirements. The number of fringes and the radial coverage can be configured around the main distribution range of the active region's optical field to ensure effective modulation of the main transverse modes. At this stage, waveguide mode field simulation and three-dimensional electromagnetic simulation tools can be used to optimize different parameter combinations, resulting in a grating layout that balances process feasibility and optical performance.

[0084] After completing the grating parameter design, the basic epitaxial structure of the vertical-cavity surface-emitting laser (VCSEL) can be fabricated. Specifically, a single-crystal substrate with a lattice match to the target epitaxial material system, such as a gallium arsenide (GaAs) substrate or an indium phosphide (IPT) substrate, can be selected. The substrate is then subjected to conventional chemical cleaning to remove surface contaminants and the native oxide layer. After drying, it is loaded into a molecular beam epitaxy (MBE) device or a metal-organic chemical vapor deposition (MOCVD) device. On the clean substrate, alternating layers of materials with different refractive indices are grown, such as high-refractive-index and low-refractive-index material layers, to form a lower distributed Bragg (DBR). The thickness of each layer in the lower DBR can be set according to the design wavelength and phase-matching conditions to obtain the required reflection bandwidth and reflectivity. On the lower DBR, an active region structure is formed through epitaxial growth. This structure can include an active region consisting of an alternating lower confinement layer, multiple quantum wells, and barrier layers, as well as an upper confinement layer. The quantum well material and thickness are selected according to the target emission wavelength and gain requirements.

[0085] Subsequently, an upper distributed Bragg mirror (DBR) is epitaxially grown above the active region. This upper DBR is formed by alternating layers of high and low refractive index materials, with a slightly fewer overall layer count than the lower DBR, to balance reflection performance and light coupling. Preferably, the top layer of the upper DBR is designed to be suitable for subsequent patterning, such as a semiconductor material similar to the grating material. In embodiments requiring an oxide confinement layer, a high-aluminum content material layer can be grown at a predetermined location on or below the upper DBR. Subsequently, lateral selective oxidation is used to form oxide holes for defining current injection and light field distribution.

[0086] After completing the basic epitaxial structure, an elliptical wheel-shaped grating can be integrated on the light-emitting side surface of the upper DBR. After cleaning and drying the sample surface, photoresist is coated on the top layer of the upper DBR or the transparent dielectric layer covering it. Electron beam lithography, deep ultraviolet lithography, or other lithography methods with sufficient resolution are used to transfer the pre-designed elliptical wheel-shaped grating pattern into the photoresist.

[0087] The grating pattern includes a central elliptical region and radially distributed circumferential stripes extending radially around this elliptical region. During layout design, the symmetry of the stripes along both the major and minor axes can be ensured simultaneously. After photolithography exposure and development, a photoresist mask corresponding to the outlines of the elliptical central region and the radial stripe region is formed on the sample surface. Using this photoresist pattern as a mask, dry etching processes such as reactive ion etching (RIE) and inductively coupled plasma (ICP-POP) etching can be employed to etch the top layer material of the DBR. The etching depth is preferably controlled within the top layer material to form the desired stripe etching grooves or step structures, while avoiding etching into the underlying layers to ensure the overall optical performance of the mirror.

[0088] During etching, the process window can be controlled by etching rate calibration and endpoint monitoring to ensure that the stripe period, linewidth, and gap are close to the design values, and the stripe sidewall contours are smooth. After etching, residual photoresist is removed by plasma ashing or wet stripping, and the sample is cleaned to remove etching residues, so that the elliptical central region and the radiating stripe region form a clear physical outline on the upper DBR surface. If the epitaxial structure contains an oxide confinement layer with high aluminum content, the sample can also be placed in an oxidation furnace at an appropriate stage to form annular or approximately elliptical oxide regions in the layer through lateral selective oxidation. The retained unoxidized opening region is preferably substantially concentric with the elliptical central region on the upper surface in the plane, which is used to limit the current injection and the lateral distribution of the master mode optical field.

[0089] After completing the grating structure, electrode fabrication, chip dicing, and packaging can be performed using conventional VCSEL processes. For example, a lower electrode with an ohmic contact can be deposited and annealed on the back side of the substrate, while an upper electrode is formed on the upper DBR surface or in the grating gap region through metal deposition and patterning. The electrode shape can avoid the main light-emitting area of ​​the grating to reduce shading and absorption. The wafer is then diced and selected, and individual chips are assembled onto a packaging substrate or system board using wire bonding, flip-chip bonding, or eutectic bonding to form packaging forms suitable for different application scenarios.

[0090] For example, the vertical-cavity surface-emitting laser preferably operates at an emission wavelength of approximately 850 nm, corresponding to an epitaxial material system of GaAs / AlGaAs. The lower distributed Bragg reflector can be formed by alternating stacks of approximately 30–35 pairs of GaAs / AlGaAs layers with different refractive indices, and the upper distributed Bragg reflector can be formed by approximately 20–25 pairs of GaAs / AlGaAs layers to obtain the desired reflectivity and intracavity field distribution near the target wavelength. In this embodiment, the oxide confinement layer is preferably an AlGaAs layer with a high aluminum content, such as Al_0.9GaAs with an aluminum content of approximately 0.9, which forms annular or nearly elliptical oxide regions through lateral selective oxidation. The unoxidized openings are used to define the current injection aperture and the lateral dimension of the dominant mode optical field.

[0091] In conjunction with the aforementioned epitaxial structure, the geometric dimensions of the elliptical wheel-shaped grating can be set according to the target beam quality and polarization characteristics. For example, the typical dimensions of the elliptical central region along the minor axis can be selected in the range of approximately 0.5 μm to 3 μm, and the typical dimensions along the major axis can be selected in the range of approximately 1 μm to 8 μm, so that the ratio between the major and minor axes falls within the aforementioned preferred range, thereby forming significant geometric anisotropy in the plane. The grating characteristic period (fringe center spacing or equivalent period) of the radiating fringe region arranged around the elliptical central region can be designed to be approximately 200 nm to 350 nm, in order to balance the diffraction coupling efficiency and process resolution requirements near the 850 nm wavelength. At this size scale, considerable additional loss differences can be introduced on the light-emitting side for different polarizations and different lateral modes, while it can be achieved through conventional deep ultraviolet lithography or electron beam lithography processes on existing GaAs / AlGaAs VCSEL process platforms. Those skilled in the art can make appropriate adjustments to the number of layer pairs, ellipse size and grating period within the above numerical range according to specific product requirements, which still belong to the variations and equivalent forms of the technical solution described in this invention.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A grating structure for a vertical-cavity surface-emitting laser, characterized in that, include: The central region is elliptical in shape and has a major axis and a minor axis that are perpendicular to each other, with the length of the major axis being greater than the length of the minor axis. as well as The radial stripe region is composed of multiple stripe structures distributed around the periphery of the central region; The plurality of stripe structures extend radially outward along the central region and are arranged periodically in the circumferential direction; The central region and the radial stripe region together define a structural distribution with geometric anisotropy.

2. The grating structure for a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The ratio of the major axis length to the minor axis length of the central region is 1.2:1 to 5:1; The plurality of stripe structures are symmetrically distributed along the long axis and the short axis.

3. The grating structure for a vertical-cavity surface-emitting laser according to claim 2, characterized in that, The period of the radial stripe region is distributed in a non-linear gradient along the radial direction. From the outer periphery of the central region outward, the period of the stripe structure gradually increases or decreases.

4. The grating structure for a vertical-cavity surface-emitting laser according to claim 1, characterized in that, The ratio of the width of the stripe structure to the gap width between adjacent stripe structures is 0.3:1 to 0.8:

1.

5. A vertical-cavity surface-emitting laser, characterized in that, include: A substrate, a lower distributed Bragg mirror, an active region, and an upper distributed Bragg mirror are stacked together. as well as A grating structure integrated into the light-emitting side surface of the upper distributed Bragg mirror; The grating structure is the grating structure as described in any one of claims 1 to 4, and the central region of the grating structure is arranged correspondingly to the center of the active region.

6. The vertical-cavity surface-emitting laser according to claim 5, characterized in that, The upper distributed Bragg mirror comprises alternating layers of first and second refractive index materials. The grating structure is formed in the topmost material layer of the upper distributed Bragg mirror, and the grating structure and the upper distributed Bragg mirror are integrally formed.

7. The vertical-cavity surface-emitting laser according to claim 5, characterized in that, The vertical cavity surface-emitting laser further includes an oxide confinement layer located between the upper distributed Bragg mirror and the active region, the oxide confinement layer having oxide holes for confining the current injection path; The center of the oxide hole is concentrically aligned with the central region of the grating structure, and the central region of the grating structure completely covers the projection area of ​​the oxide hole in the light emission direction.

8. The vertical-cavity surface-emitting laser according to claim 5, characterized in that, The grating structure includes multiple etching grooves, the depth of which is less than the thickness of the topmost material layer of the upper distributed Bragg mirror, so that the topmost material layer retains a continuous material layer of a predetermined thickness at the bottom of the etching groove.

9. A method for beam shaping of a vertical-cavity surface-emitting laser array, characterized in that, The array comprises a plurality of vertical-cavity surface-emitting lasers as described in any one of claims 5 to 8, and the method comprises: The far-field light intensity distribution data of the array is collected on a preset projection plane; In a coordinate system with the major and minor axes of the elliptical spot of each vertical cavity laser as the main directions, a two-dimensional elliptical anisotropic multi-scale transformation is performed on the far-field intensity distribution data to obtain an elliptical anisotropic coefficient matrix. The wavelet basis function of the multi-scale transformation has different scale parameters in the direction corresponding to the major axis and the direction corresponding to the minor axis. Based on the elliptic anisotropy coefficient matrix, the coefficients in each scale sub-band are divided according to the position of the vertical cavity surface-emitting laser in the array to obtain the elliptic anisotropy eigenvector corresponding to each vertical cavity surface-emitting laser. Based on the preset target illumination distribution and / or target polarization distribution, construct the target elliptic anisotropic eigenvector, and use the driving intensity of each vertical cavity surface laser as the optimization variable to establish an optimization model with elliptic anisotropic eigenvalue constraints and sparse constraints. Solve the optimization model to obtain the driving intensity solution vector corresponding to each vertical cavity surface emitter (VCSEL), and control the switching state, driving current and / or driving duty cycle of each VCSEL in the array according to the driving intensity solution vector.

10. The method according to claim 9, characterized in that, The step of performing a two-dimensional elliptic anisotropic multi-scale transformation on the far-field light intensity distribution data to obtain the elliptic anisotropic coefficient matrix includes: Based on the geometric arrangement of each vertical cavity surface-emitting laser in the array, determine the center position of the reference spot on the preset projection plane for each emitting unit; Construct a set of elliptical window functions centered on the center positions of each reference spot; The far-field light intensity distribution data is weighted with each elliptical window function and a local two-dimensional elliptical anisotropic multi-scale transformation is performed in the corresponding local coordinate system to obtain the local elliptical anisotropic coefficient submatrix assigned to the corresponding emission unit. The local elliptical anisotropic coefficient submatrices are then concatenated according to the array index dimension to form the elliptical anisotropic coefficient matrix.

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