Metasurface design method, device, equipment and storage medium

Abstract

The present application provides a metasurface design method, device, equipment and storage medium. It relates to the technical field of diffraction optical element design. The method includes: introducing a grating structure on the basis of the GS algorithm to obtain a GS algorithm model based on the grating diffraction order, and using the GS algorithm model based on the grating diffraction order to obtain the sampling point position of the target surface; constructing a multi-angle structure database under a complex light field; based on the sampling point position of the target surface and the multi-angle structure database under a complex light field, reverse design of the metasurface characteristics is performed to obtain the metasurface structure. By introducing an improved GS algorithm based on the metasurface characteristics and a multi-angle structure database under a complex light field, the present application ensures that the metasurface can still accurately modulate the phase under multi-angle incidence in a complex light field, thereby achieving structured light with low uniformity error and high diffraction efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of diffractive optical element design, and in particular to a metasurface design method, device, equipment and storage medium. Background Art

[0002] With the development of optical technology, the application of structured light has covered areas such as face recognition, gesture recognition, projectors, three-dimensional contour reconstruction (3D), depth measurement, anti-counterfeiting identification, etc. Therefore, the demand for efficient structured light projector design has increased. This is specifically reflected in the improvement of performance such as small size, high design optimization efficiency, low uniformity error of output light, and large viewing angle. The structured light projection module in the existing technology mainly includes vertical cavity surface lasers (VCSELs), collimating lenses, and diffraction optical elements (DOE). Because they are discrete components, the entire module occupies a large space and has low alignment accuracy. In addition, the traditional DOE has a large unit size, which limits the field of view and dot density, reducing its application value in commercial three-dimensional imaging systems. Metasurface, with its sub-wavelength characteristic size, provides an efficient phase modulation method that can significantly improve the field of view, dot density and diffraction efficiency, and improve integration.

[0003] However, existing research has largely focused on using metasurfaces to generate structured light for plane waves with normal incidence, without fully considering the multi-angle incidence of complex light fields. When using metasurfaces with VCSEL arrays to generate structured light, due to the large divergence angle of the VCSEL array, if the metasurface is still designed for normal incidence under multi-angle incidence conditions, it will result in low diffraction efficiency and high uniformity errors. Summary of the Invention

[0004] This application provides a metasurface design method, apparatus, device, and storage medium designed to reduce the number of parameters and computational complexity required for remote sensing image target detection models in complex scenes. By introducing an improved GS algorithm based on metasurface properties and a database of multi-angle structures in complex light fields, the metasurface ensures accurate phase modulation under multi-angle incidence in complex light fields, thereby achieving structured light with low uniformity error and high diffraction efficiency. By designing a metasurface that integrates collimation and beam splitting, the application eliminates the need for additional collimating lenses, achieving a more compact optical system design and significantly reducing system size. The proposed diffractive optical element design method abandons reliance on traditional design flow methods based on particle swarms and genetic algorithms. Instead, it utilizes pre-simulated data to generate a metasurface property database. The improved GS algorithm is then used to numerically optimize the metasurface structure, significantly reducing computational complexity and accelerating optimization. This strategy enables rapid and accurate complex amplitude modulation, even for large or complex diffractive structures, effectively improving design flexibility and responsiveness. It is particularly suitable for modern optical applications requiring rapid iteration and high precision.

[0005] This application can not only be applied to the design of any diffraction optical element such as structured light, flat-top light generation, and hologram production, but also provide efficient optical solutions for fields such as augmented reality (AR), virtual reality (VR), and intelligent sensing.

[0006] In a first aspect, the present application provides a metasurface design method, comprising:

[0007] On the basis of GS algorithm, a grating structure is introduced to obtain a GS algorithm model based on grating diffraction orders, and the sampling point position of the target surface is obtained by using the GS algorithm model based on grating diffraction orders;

[0008] Construct a multi-angle structure database under complex light fields;

[0009] Based on the sampling point positions of the target surface and a multi-angle structure database under a complex light field, reverse design of the metasurface characteristics is performed to obtain the metasurface structure.

[0010] In one possible design, the sampling point positions of the target surface include sampling point coordinates of the DOE surface and sampling point coordinates of the image plane. The sampling point positions of the target surface are obtained using a GS algorithm model based on grating diffraction orders, including:

[0011] The sampling point coordinates of the DOE surface are represented by (m0, n0), and the total number of sampling points on the DOE surface is M*N; where m0 and n0 are the m0th row and n0th column of the discrete phase within a single grating period, and M and N are the M and N values ​​of the phase discrete within the horizontal axis and the vertical axis within a single grating period, respectively.

[0012] The sampling point coordinates of the image plane are represented by (m, n), and the total number of sampling points in the image plane is M*N; where m and n are the diffraction orders in two directions of the two-dimensional grating when the plane light is normally incident.

[0013] In one possible design, a multi-angle structure database under complex light fields is constructed, including:

[0014] The relationship between the structural parameters and the modulation phase is described based on the following functional relationship:

[0015] φ i =f i (R)

[0016] Where R is the elementary structure parameter; i is the i-th diffraction order; φ i represents the modulation phase corresponding to the elementary structure parameters under the i-th diffraction order;

[0017] According to the functional relationship, the mapping relationship between the nanorods and the phase at different incident angles is obtained; and based on the mapping relationship between the nanorods and the phase at different incident angles, a multi-angle structure database under complex light fields is constructed.

[0018] In one possible design, based on the sampling point positions of the target surface and a database of multi-angle structures under complex light fields, reverse design of the metasurface characteristics is performed to obtain the metasurface structure, including:

[0019] The target amplitude is combined with a random phase symmetric about the x-axis and y-axis to form a complex amplitude u' on the image plane. i ;

[0020] The complex amplitude is processed by inverse Fourier transform to generate the complex amplitude of the DOE surface;

[0021] Based on the phase information extracted from the complex amplitude of the DOE surface, the DOE phase information is restored through the correspondence between the nanorods and the phase under normal incidence. The structural parameters of the metasurface are obtained; where R(m0,n0) represents the parameters related to the nanopillar and the phase, and φ(m0,n0) represents the discrete phase of the m0th row and n0th column. It represents the correspondence between the phase of a plane wave and the parameters of the nanopillars when the plane wave is incident normally. It is part of the multi-angle structure database under complex light fields.

[0022] Using φ i '(m0,n0)=f i (R(m0,n0)) calculates the phase modulation effect of the metasurface at different incident angles and superimposes the phase factor ψ caused by the oblique incidence of plane light i , and the total phase φ of the diffraction surface is obtained i ", the calculation formula is:

[0023]

[0024] Among them, φ i ' is the phase modulation produced by the metasurface when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence, L x is the horizontal axis length of a single grating period, L y is the ordinate length of a single grating period;

[0025] The complex amplitude of the diffraction surface can be expressed as exp(iφ i ”(m0,n0)), by Fourier transforming the complex amplitude, we can get the complex amplitude distribution u of each diffraction order in the far field. i ”(m0,n0), the calculation formula is:

[0026] u i”(m0,n0)=FFT(exp(iφ i ”(m0,n0)))

[0027] Where, FFT represents Fourier transform, exp represents exponential function;

[0028] The objective function is constructed with the goal of optimizing the matching degree between the far-field diffraction order amplitude and the target diffraction order amplitude at different incident angles:

[0029] FoM i (m,n)=(u i ”(m,n)-A Ti (m,n)) 2

[0030] Where A Ti (m,n) is the target amplitude distribution when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence, FoM i (m,n) is the value of the objective function when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence, u” i "(m,n) is the complex amplitude distribution of each diffraction order in the far field after being modulated by the metasurface when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence;

[0031] The DOE surface phase φ is calculated by the objective function i "The derivative of the phase gradient is obtained, and the gradient expression of the objective function with respect to the DOE surface phase is:

[0032]

[0033] Where, Indicates u" i conjugation, Indicates A Ti The conjugate of (m,n), real means taking the real part, and conj means taking the conjugate;

[0034] According to the relationship between phase and nanorod geometric parameters φ = f i (R), the gradient of the objective function value with respect to the nanopillar radius is calculated by the following formula:

[0035]

[0036] Using the gradient of the objective function value with respect to the nanopillar radius, the nanopillar radius R(m0,n0) is updated using the maximum-minimum method in each iteration. The update formula is:

[0037]

[0038] Where k is the gradient learning rate factor, and max is the maximum value function;

[0039] After obtaining the preliminary optimized metasurface parameters, the phase modulation of the metasurface is obtained by the formula φ(m0,n0)=f0(R(m0,n0)) under normal incidence; the amplitude A0(m0,n0)=1 is set, and the complex amplitude distribution of each diffraction order in the image plane is obtained by Fourier transform. In each iteration, the phase part of the obtained complex amplitude of each diffraction order in the image plane is retained, and the amplitude part is replaced by the target complex amplitude and multiplied by the amplitude correction factor e. This process is repeated until the predetermined number of iterations is reached or the diffraction efficiency and uniformity of the target diffraction order meet the design requirements, and the iteration is stopped to obtain the final metasurface structure.

[0040] In one possible design, after performing reverse design of metasurface characteristics based on the sampling point positions of the target surface and a database of multi-angle structures under complex light fields to obtain the metasurface structure, the method further includes:

[0041] The grating phase and the collimation phase are superimposed to obtain a phase that realizes the integration of collimation and beam splitting at the same time; wherein the expression of the collimation phase is:

[0042]

[0043] Where, Collimating Phase is the collimation phase, λ is the wavelength, r imn is the distance between the phase of the mth row and nth column of the DOE surface and the origin of the DOE surface, and f is the effective focal length, which is expressed as:

[0044]

[0045] Where L1 is the distance between the VCSELs array and the metasurface, L2 is the thickness of the metasurface substrate, and n is the refractive index of the substrate.

[0046] Phase and function that will simultaneously realize the integration of collimation and beam splitting By correspondingly performing the above steps, we obtain a metasurface that realizes the integration of collimation and beam splitting at the same time.

[0047] In one possible design, after reverse engineering the metasurface characteristics based on the sampling point positions of the target surface and a multi-angle structure database under a complex light field to obtain the metasurface structure, the method further includes designing a protective layer and an anti-reflection film; wherein the thickness of the protective layer is determined by the thickness corresponding to the optimal diffraction efficiency and uniformity within a single period; and the anti-reflection film includes a first anti-reflection film and a second anti-reflection film connected to each other, the refractive index of the second anti-reflection film being higher than the refractive index of the protective layer, and the refractive index of the first anti-reflection film being lower than the refractive index of the protective layer.

[0048] In a second aspect, the present application provides a metasurface design device, comprising:

[0049] The position matching module is configured to introduce a grating structure on the basis of the GS algorithm to obtain a GS algorithm model based on the grating diffraction order, and use the GS algorithm model based on the grating diffraction order to obtain the sampling point position of the target surface;

[0050] A database construction module is configured to construct a multi-angle structure database under a complex light field;

[0051] The iterative design module is configured to perform reverse design of the metasurface characteristics based on the sampling point positions of the target surface and a multi-angle structure database under a complex light field to obtain the metasurface structure.

[0052] In a third aspect, an embodiment of the present application provides an electronic device comprising: at least one processor and a memory; the memory stores computer-executable instructions; the at least one processor executes the computer-executable instructions stored in the memory, so that the at least one processor executes the metasurface design method described in the first aspect and various possible designs of the first aspect.

[0053] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions. When a processor executes the computer-executable instructions, the metasurface design method described in the first aspect and various possible designs of the first aspect is implemented.

[0054] In a fifth aspect, an embodiment of the present application provides a computer program product, including a computer program. When the computer program is executed by a processor, it implements the metasurface design method described in the first aspect and various possible designs of the first aspect.

[0055] The main advantages of the metasurface design method, device, equipment, and storage medium provided in this application are summarized as follows:

[0056] (1) Traditional diffractive optical element (DOE) design methods rely on full-wave simulation for optimization, and usually calculate gradients through adjoint optimization to simulate the impact of changes in element parameters on optical response. Although this method is accurate, due to the complexity of full-wave simulation, especially in large-scale DOE design, the computational complexity is huge and time-consuming. Each iteration requires forward and adjoint full-structure simulation, which is extremely challenging for the optimization of large-scale or complex diffractive optical elements. To solve the above problems, this application uses the phase response of nanopillars under different light fields to construct a diffractive optical element characteristic database. Through a one-time full-wave simulation, the phase modulation response of the nanopillars under different incident angles is obtained and recorded in the phase database. The optical properties of the nanopillars (such as the influence of geometric parameters on phase modulation) are stored in numerical form. The response of each nanopillar can be regarded as a complex amplitude modulation of the incident light field, and these values ​​can be directly used in the subsequent optimization process without the need for repeated full-wave simulation. In the subsequent design iteration process, the pre-constructed database is used to obtain the complex amplitude modulation characteristics of the nanopillars under different design conditions through numerical interpolation. These numerical properties can be directly incorporated into the calculation of the complex amplitude without having to re-run a full-wave simulation. This improvement transforms the time-consuming full-wave simulation step in traditional DOE design into a highly efficient numerical optimization, significantly increasing design speed and ensuring phase modulation accuracy in complex optical field environments, making large-scale design or complex structure optimization possible.

[0057] (2) Traditional diffractive optical elements (DOEs) have a small field of view, low lattice density, high-order diffraction, and uneven energy distribution across diffraction orders due to their large unit size, resulting in low overall efficiency. This application overcomes these problems by using metasurfaces with subwavelength feature sizes, achieving structured light generation with a wider field of view and higher density.

[0058] (3) Traditional metasurface design methods are usually designed for normally incident light. When incident at multiple angles in a complex light field, traditional metasurface designs have the problem of phase shift, resulting in inaccurate phases at different incident angles, which in turn affects the imaging results. This application introduces an improved GS algorithm based on metasurface characteristics, integrating obliquely incident nanopillars with a phase database and protective layer characteristics, so that the metasurface can still maintain the accuracy of phase modulation under complex light field multi-angle incident conditions, thereby ensuring high-precision imaging effects, while improving the diffraction efficiency of structured light and reducing uniformity errors.

[0059] (4) Conventional diffractive optical elements require the addition of collimating lenses, which significantly increases the size and complexity of the system. This application eliminates the need for additional collimating lenses by designing a metasurface that integrates collimation and beam splitting, achieving a more compact optical system design and significantly reducing the system size. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0061] Figure 1 Schematic diagram of the positions of the DOE surface and the image plane provided in the embodiment of the present application;

[0062] Figure 2 Schematic diagram of the multi-angle structure database under complex light fields provided by the embodiments of the present application; (a) is a graph showing the corresponding relationship between nanopillar parameters (radius) and phase; (b) is a graph showing the corresponding relationship between nanopillar parameters (radius) and transmittance;

[0063] Figure 3 A flowchart of a reverse design method based on metasurface characteristics provided in an embodiment of the present application;

[0064] Figure 4 This is the spatial distribution diagram of the light field after the VCSEL array provided in the embodiment of the present application is phase modulated and propagated for 1m;

[0065] Figure 5 Comparison diagrams of the beam splitting effects of the conventional method and the present method provided in the embodiments of the present application; wherein (a) is a comparison diagram of the beam splitting effects of the conventional method and the present method for the intensity distribution of each diffraction order at normal incidence; (b) is a comparison diagram of the beam splitting effects of the conventional method and the present method for the intensity distribution of each diffraction order at an oblique incidence of 12.93° in the x-direction; (c) is a comparison diagram of the beam splitting effects of the conventional method and the present method for the intensity distribution of each diffraction order at an oblique incidence of 16.05° in the y-direction;

[0066] Figure 6 Comparison diagrams of the gradients of the conventional method and the present method provided in the embodiments of the present application; (a) is a comparison diagram of the gradient distribution at normal incidence; (b) is a comparison diagram of the gradient distribution at an oblique incidence of 12.93° in the x-direction; (c) is a comparison diagram of the gradient distribution at an oblique incidence of 16.05° in the y-direction;

[0067] Figure 7 Comparison of the structured light performance of the conventional method and the present method provided in the embodiments of the present application; wherein (a) is a schematic diagram showing how the uniformity error varies with the oblique incident angle; (b) is a schematic diagram showing how the diffraction efficiency varies with the oblique incident angle;

[0068] Figure 8Schematic diagram of the metasurface structure provided in an embodiment of the present application and a schematic diagram of the diffraction efficiency and uniformity error of structured light with different protective layer thicknesses at normal incidence; (a) is a schematic diagram of the metasurface structure; (b) is a schematic diagram of the diffraction efficiency and uniformity error of structured light with different protective layer thicknesses at normal incidence;

[0069] Figure 9 Figure 2 shows the diffraction efficiency and uniformity error of structured light with different anti-reflection film thicknesses under normal incidence provided by the embodiments of the present application. (a) is a schematic diagram of a metasurface structure with a double-layer anti-reflection film; (b) is a schematic diagram showing how the transmittance varies with the two layers of anti-reflection film; (c) is a schematic diagram showing how the uniformity error (UE) varies with the two layers of anti-reflection film; and (d) is a schematic diagram showing how the diffraction efficiency varies with the two layers of anti-reflection film.

[0070] Figure 10 Schematic diagrams of the application of integrated metagrating and collimation provided in the embodiments of the present application; (a) schematic diagram of a single-sided metasurface with both beam splitting and collimation functions; (b) schematic diagram of a single-sided metasurface with both beam splitting and collimation functions;

[0071] Figure 11 This is a schematic diagram of the structure of the metasurface design device provided in an embodiment of the present application.

[0072] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0073] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0074] In the technical solution of this application, the collection, storage, use, processing, transmission, provision and disclosure of information such as financial data or user data involved comply with the provisions of relevant laws and regulations and do not violate public order and good morals.

[0075] It should be noted that in the embodiments of the present application, certain software, components, models and other existing solutions in the industry may be mentioned. They should be regarded as exemplary. Their purpose is only to illustrate the feasibility of implementing the technical solution of the present application, but it does not mean that the applicant has or will necessarily use the solution.

[0076] The following specific embodiments describe in detail the technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0077] The embodiment of the present application provides a metasurface design method, which begins with step S10, designing a GS algorithm based on grating diffraction orders.

[0078] In this embodiment, a grating structure is introduced on the basis of the traditional GS algorithm to achieve the beam splitting effect. The grating design is based on the precise control of different diffraction angles and corresponding phases, so that even in the case of large-angle beam splitting, the sampling point position on the target surface can be better matched with the actual physical position. The principle of the GS algorithm based on grating diffraction order is as follows:

[0079] The sampling point coordinates of the DOE surface are represented by (m0, n0), and the total number of sampling points on the DOE surface is M*N; where m0 and n0 are the m0th row and n0th column of the discrete phase within a single grating period, and M and N are the phase discrete values ​​in the horizontal axis and the phase discrete values ​​in the vertical axis within a single grating period, respectively; the sampling point coordinates of the image plane are represented by (m, n), and the total number of sampling points on the image plane is M*N; where m and n are the diffraction orders in two directions of the two-dimensional grating when the plane light is normally incident.

[0080] Step S20: construct a multi-angle structure database under a complex light field.

[0081] In previous studies, full-wave electromagnetic simulation methods (such as the finite-difference time-domain method (FDTD), the finite element method (FEM), and rigorous coupled wave analysis (RCWA) and other numerical calculation methods) are usually used to design and optimize metasurfaces for structured light modulation. These methods generally assume that the incident light is vertically incident. In this case, researchers adjust the size or shape of the nanopillars to achieve corresponding phase modulation (such as geometric phase, transmission phase, etc.). By selecting different primitive structures, phase coverage in the range of 0 to 2π can be achieved, thereby achieving precise control of the output light.

[0082] However, in real-world applications, such as when light from vertical-cavity surface-emitting lasers (VCSELs) or photonic crystal surface-emitting lasers (PCSELs) is collimated and incident on a two-dimensional grating surface, not all rays are incident perpendicularly. Furthermore, because the angle of the incident light can vary, the phase response curves of the same nanopillars under different incidence conditions can vary significantly. Consequently, traditional design methods based on the assumption of perpendicular incidence may not accurately predict the beam modulation effect under real-world conditions.

[0083] In practical applications, incident light often occurs at a variety of angles. This requires designers to consider not only perpendicular incidence but also the phase response of the same nanopillar at different incident angles when designing metasurfaces. This comprehensive consideration of multiple angles is crucial for accurately predicting and optimizing beam splitting effects.

[0084] During the design process, we selected the scanning incident angle as the 1st to nth order diffraction angle of the designed grating structure when the light is perpendicularly incident to ensure the sampling spacing requirements. To better describe the relationship between the element structure parameters and the modulation phase, we defined the following functional relationship:

[0085] φ i =f i (R)

[0086] in:

[0087] R is the parameter of the elementary structure, such as size, shape or material properties;

[0088] i is the i-th diffraction order;

[0089] It represents the modulation phase corresponding to the elementary structure parameters at the i-th diffraction order.

[0090] Through the above functional relationship, this embodiment can obtain the mapping relationship between nanorods and phases at different incident angles. Figure 2 As shown, in order to make the phase modulation more accurate, the nanorods that will produce strong coupling are removed and the nanorods with a transmittance greater than 90% are selected.

[0091] Step S30: reverse design based on metasurface characteristics.

[0092] like Figure 3 The figure shows the flow chart of the inverse design method based on the characteristics of the metasurface. This process starts by synthesizing the target amplitude and the random phase symmetric about the x-axis and y-axis into a complex amplitude u on the image plane. i', where the initial e factor is set to a constant of 1. This complex amplitude is processed by inverse Fourier transform to generate the complex amplitude of the DOE surface. Subsequently, the phase information extracted from the complex amplitude of the DOE surface is used to restore the DOE phase information through the correspondence between the nanopillars and the phase under normal incidence. Obtain the structural parameters of the metasurface.

[0093] Then use φ i '(m0,n0)=f i (R(m0,n0)) calculates the phase modulation effect of the metasurface at different incident angles, and on this basis superimposes the phase factor ψ caused by the oblique incidence of plane light i , and the total phase φ of the diffraction surface is obtained i ”, the formula is:

[0094]

[0095] Among them, φ i ' is the phase modulation produced by the metasurface when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence, L x is the horizontal axis length of a single grating period, L y is the ordinate length of a single grating period.

[0096] Since the incident light is a plane wave, its amplitude is considered to be a constant of 1. Therefore, the complex amplitude of the diffraction surface can be expressed as exp(iφ i ”(m0,n0)), by Fourier transforming the complex amplitude, we can get the complex amplitude distribution u of each diffraction order in the far field. i ”(m0,n0), that is:

[0097] u i ”(m0,n0)=FFT(exp(iφ i ”(m0,n0)))

[0098] Where FFT represents Fourier transform, and exp represents exponential function.

[0099] In order to optimize the matching degree between the far-field diffraction order amplitude and its target diffraction order amplitude at different incident angles, the objective function is defined as:

[0100] FoM i (m,n)=(u i ”(m,n)-A Ti (m,n)) 2

[0101] Where A Ti (m,n) is the target amplitude distribution when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence, FoM i(m,n) is the value of the objective function when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence, u i "(m,n) is the complex amplitude distribution of each diffraction order in the far field after being modulated by the metasurface when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence;

[0102] Among them, A Ti is the target amplitude distribution, FoM i Next, the DOE surface phase φ is calculated by the objective function. i The derivative of ” is used to obtain the corresponding phase gradient. This gradient is used to guide the next step of metasurface optimization. After derivation, the gradient expression of the objective function with respect to the DOE surface phase is:

[0103]

[0104] Where, Indicates u" i conjugation, Indicates A Ti The conjugate of (m,n), real means taking the real part, and conj means taking the conjugate;

[0105] According to the relationship between phase and nanorod geometric parameters φ = f i (R), the gradient of the objective function with respect to the nanopillar radius is calculated by the chain rule:

[0106]

[0107] Using this gradient, the nanopillar radius R(m0,n0) is updated using the maximum-minimum method in each iteration. The update formula is:

[0108]

[0109] Where k is the gradient learning rate factor and max is the maximum value function.

[0110] Where k is the gradient learning rate factor. After obtaining the preliminary optimized metasurface parameters, the phase modulation of the metasurface is obtained by the formula φ(m0,n0)=f0(R(m0,n0)) under normal incidence. Since a periodic structure is used, the light incident on a single periodic structure can be approximated as a plane wave, so the amplitude A0(m0,n0)=1 is set, and the complex amplitude distribution of each diffraction order in the image plane is obtained through Fourier transform. In each iteration, the phase portion of the obtained complex amplitude of each diffraction order in the image plane is retained, while the amplitude portion is replaced with the target complex amplitude and multiplied by the amplitude correction factor e to improve the uniformity of each target diffraction order. This process is repeated until the predetermined number of iterations is reached or the diffraction efficiency and uniformity of the target diffraction order meet the design requirements, and the final metasurface structure is obtained.

[0111] Step S40: designing a protective layer and an anti-reflection film.

[0112] This embodiment proposes the effect of the protective layer thickness on the diffraction efficiency and uniformity of the metagrating. When the thickness of the protective layer changes from short to long, the diffraction efficiency shows a periodic change. Therefore, the protective layer thickness with the best diffraction efficiency and uniformity within a single period is selected. This embodiment proposes the use of a double-layer anti-reflection film for anti-reflection, such as Figure 9 As shown, in order to improve diffraction efficiency, the refractive index of the second antireflection film 2 in the double-layer antireflection film is higher than that of the protective layer, and the refractive index of the first antireflection film 1 is lower than that of the protective layer of the antireflection film.

[0113] The following examples of this application will further illustrate the feasibility and progress of the present invention in conjunction with a specific implementation case.

[0114] In this specific implementation case, the metasurface design method includes the following steps:

[0115] Step 1. Determine the metasurface parameter structure.

[0116] Based on the size of the VCSEL array (465×572um) and the maximum beam splitting angle required for the structured light in the x and y directions, the two-dimensional plane orthogonal grating equation and the beam splitting characteristics of the metasurface were used to determine L1=1.775mm, L2=0.675mm, Px=Py=400nm, M=17, and N=21. The light field distribution of the VCSEL array after passing through the metasurface at a distance of 1m is shown in the figure below. Figure 4 shown.

[0117] Step 2. Build a multi-angle structure database under complex light fields.

[0118] Using Si as the nanopillar material, with a height of 658 nm and a BF33 (SiO2) substrate, the researchers calculated the phase modulation of nanopillars with radii ranging from 50 nm to 160 nm under plane wave incidence at various angles. The results show that nanopillars can achieve a phase range of 0 to 2 pi by varying their radius at various angles of incidence. To eliminate phase modulation inaccuracies caused by strong coupling, meta-atoms of corresponding sizes, where phase changes with radius abruptly change, were removed from the curves. This resulted in a database of the phase modulation variation of nanopillars at different angles of incidence.

[0119] Step 3. Calculate the metasurface structure using the improved GS algorithm based on metasurface properties

[0120] The obtained grating period parameters Px, Py, sampling numbers M, N, and target diffraction order amplitude distribution AT are loaded into the traditional GS algorithm based on grating structure along with the multi-angle structure database under complex light field. The DOE surface phase generated by the traditional GS algorithm modulates the intensity distribution of each diffraction order on the image plane under normal incidence and oblique incidence in the x and y directions (to meet the sampling law, the oblique incidence angle in the x direction is selected to be 12.93° and the oblique incidence angle in the y direction is selected to be 16.05°) as shown in the figure. Figure 5 As shown in Figure 1, the diffraction efficiency can exceed 0.88, but the uniformity error is large, exceeding 0.3. The diffraction efficiency (EFF) is calculated as the ratio of the power of the target diffraction order to the power entering the DOE surface, and the uniformity error is calculated as:

[0121]

[0122] Where W order Represents the light intensity of each diffraction order.

[0123] This high uniformity error may cause recognition errors in 3D reconstruction applications.

[0124] In contrast, when the improved GS algorithm based on metasurface characteristics is used, the diffraction efficiency of the structured light is further improved under the conditions of normal incidence of the plane wave and oblique incidence in the x and y directions, and the uniformity error is significantly reduced to below 0.063. This shows that the improved GS algorithm can escape the local optimal solution and has higher performance in the modulation of structured light. In order to verify whether the objective function of the improved GS algorithm based on metasurface characteristics converges with respect to the gradient of the metasurface structure parameters. Figure 6As shown in the figure, the gradient of the proposed method decreases significantly during the iteration process, indicating that the algorithm can effectively optimize the phase modulation of the metasurface, making the DOE surface phase closer to the phase distribution of the target image plane. In contrast, the gradient change of the traditional algorithm is not obvious and the convergence is poor. In order to verify whether the objective function of the improved GS algorithm based on the characteristics of the metasurface converges with respect to the gradient of the metasurface structural parameters. Figure 6 As shown in the figure, the gradient of the proposed method decreases significantly during the iteration process, indicating that the algorithm can effectively optimize the phase modulation of the metasurface, making the DOE surface phase closer to the phase distribution of the target image plane. In comparison, the gradient change of the traditional algorithm is not obvious and the convergence is poor.

[0125] Step 4. Full-wave simulation to verify the beam-splitting effect of the metasurface.

[0126] FDTD simulations were used to verify the beam splitting effect of the metasurface on plane waves at different incident angles, and to evaluate the uniformity error and diffraction efficiency. Due to the reflection between the protective layer and the air, a grating sub-analyzer was placed in the protective layer material to avoid affecting the results. Figure 7 As shown in the figure, when the incident angle is less than 9° in the x and y directions, the uniformity error of the structured light generated by the metasurface is less than 0.1, and the diffraction efficiency is greater than 0.83. Compared with the traditional design method, the diffraction efficiency is improved by about 0.02, and the uniformity error is reduced by about 0.35. However, in the ideal calculation results of the improved GS algorithm based on the metasurface, when the incident angle is obliquely 12.93° in the x direction, the diffraction efficiency is 0.9352 and the uniformity error is 0.0624; when the incident angle is obliquely 16.05° in the y direction, the diffraction efficiency is 0.9206 and the uniformity error is 0.0604. This deviation may be attributed to the weak coupling effect between the nanopillars and the transmittance of some nanopillars being less than 1. Despite this, these results still reach a high level of commercial standards.

[0127] Step 5. Select the appropriate thickness of the protective layer.

[0128] Appropriate protective layer thickness can increase transmittance, so the grating subanalyzer is placed in air to simulate the effects of protective layers of different thicknesses on the diffraction efficiency and uniformity error of the metasurface under normal incidence conditions. Figure 8 As shown in the figure, with the change of the protective layer thickness, the diffraction efficiency and uniformity error fluctuate significantly. When the protective layer thickness is 2.235μm, the diffraction efficiency and uniformity error are the best, so 2.235μm is selected as the optimal protective layer thickness. After determining the protective layer thickness, the diffraction efficiency and uniformity error of the structured light generated by the metasurface at different incident angles are as follows: Figure 8 shown.

[0129] Step 6. Select the appropriate AR coating thickness.

[0130] Using SiO2 as the material for AR coating 1 and SiN as the material for AR coating 2, the effects of protective layers of different thicknesses on the diffraction efficiency and uniformity error of the metasurface under normal incidence are simulated. Figure 9 As shown in the figure, the diffraction efficiency and transmittance show periodic changes with the thickness of AR coating 1 and AR coating 2. When the thickness of AR coating 1 is 1.125μm and the thickness of AR coating 2 is 1.125μm, the diffraction efficiency and uniformity error are better. Therefore, this thickness is selected as the optimal protective layer thickness. At this time, the diffraction efficiency reaches 85.28% and the uniformity reaches 0.0683.

[0131] Step 7. Metasurface integrating collimation and beam splitting.

[0132] (a) Metasurface with beam splitting and collimation functions.

[0133] By superimposing the grating phase optimized by the above-mentioned inverse design method based on the properties of the metasurface and the collimation phase, a phase that achieves both collimation and beam splitting can be obtained. The expression of the collimation phase is:

[0134]

[0135] Where f is the effective focal length:

[0136]

[0137] Where L1 is the distance from the VCSELs array to the metasurface, L2 is the thickness of the metasurface substrate, and n is the refractive index of the substrate.

[0138] Phase and beam splitting integrated Functions can be obtained to achieve the integration of collimation and beam splitting, such as Figure 10 As shown in (a).

[0139] In FDTD, a sampling simulation is performed on the metasurface with integrated collimation and beam splitting. The sampling simulation center is 0 μm away from the origin of the metasurface, and the size is 80.4 μm*80.4 μm. The diffraction efficiency and uniformity of Gaussian light are simulated when the distance between the origin and the metasurface is the designed focal length. The diffraction efficiency can reach 78.36% and the uniformity can reach 0.0624. The sampling simulation center is 480 μm away from the origin of the metasurface, and the size is 80.4 μm*80.4 μm. The diffraction efficiency and uniformity of the simulated Gaussian light when the distance from the origin to the metasurface is the designed focal length are obtained, and the diffraction efficiency can reach 77.24% and the uniformity can reach 0.0667; the sampling simulation center point is 480um away from the origin of the metasurface, and the size of the metasurface is 80.4um*80.4um. The diffraction efficiency and uniformity of the simulated Gaussian light when the distance from the origin is -300um and the distance from the metasurface is the designed focal length are obtained. The diffraction efficiency and uniformity are obtained, and the diffraction efficiency can reach 72.75% and the uniformity can reach 0.1266.

[0140] (b) Monolithic two-sided design of the beam-splitting metasurface and the collimating metasurface.

[0141] like Figure 10 As shown in (b), the designed beam splitting metasurface is the metagrating designed above, and the metasurface structure parameters of its collimation function are determined by the collimation phase and Functions can be obtained by corresponding.

[0142] In summary, the core innovations of the metasurface design method provided in the embodiments of the present application are reflected in the following four points:

[0143] First, solve the problems of slow design speed and inaccurate complex amplitude modulation of diffractive optical elements.

[0144] In the design of diffractive optical elements, inverse design optimization methods have been widely used. Common methods include genetic algorithms, particle swarm optimization (PSO), deep learning algorithms, and adjoint optimization algorithms. Although these methods have their own advantages in different scenarios, when faced with complex light fields or large-scale DOE designs, the amount of calculation is huge and the time consumption is long, and the optimization speed needs to be improved urgently. To solve the above problems, this embodiment proposes an inverse design method based on metasurface characteristics. This method uses the complex amplitude response of nanopillars under different light fields to construct a diffractive optical element characteristic database. Through a one-time full-wave simulation, the complex amplitude modulation response of the nanopillars under different incident angles is obtained and recorded in the complex amplitude database. The optical properties of the nanopillars (such as the influence of geometric parameters on phase modulation) are stored in numerical form. The response of each nanopillar can be regarded as a complex amplitude modulation of the incident light field. These values ​​can be directly used in the subsequent optimization process without the need for repeated full-wave simulations. In the subsequent design iteration process, the pre-constructed database is used to obtain the complex amplitude modulation characteristics of the nanopillars under different design conditions through numerical interpolation. These numerical properties can be directly incorporated into the calculation of the complex amplitude without having to re-run the full-wave simulation. This improvement transforms the time-consuming full-wave simulation step in traditional DOE design into efficient numerical optimization, greatly improving design speed and ensuring phase modulation accuracy in complex optical field environments, making large-scale design or complex structure optimization possible.

[0145] Second, solve the problems of small field of view, low dot density and low diffraction efficiency.

[0146] Traditional diffractive optical elements (DOEs) suffer from large unit cell sizes, resulting in a narrow field of view, low lattice density, high-order diffraction, and uneven energy distribution across diffraction orders, leading to low overall efficiency. This embodiment overcomes these issues by using metasurfaces with subwavelength feature sizes, enabling structured light generation with a wider field of view and higher density.

[0147] Third, solve the problems of phase shift and inaccurate imaging caused by multi-angle incidence of complex light fields.

[0148] Traditional metasurface design methods are usually designed for normally incident light. When incident at multiple angles in a complex light field, traditional metasurface designs have the problem of phase shift, resulting in inaccurate phases at different incident angles, which in turn affects the imaging results. By introducing an inverse design method based on metasurface characteristics, integrating obliquely incident nanopillars with a phase database and protective layer characteristics, the metasurface can maintain the accuracy of phase modulation under complex light field multi-angle incidence conditions, thereby ensuring high-precision imaging effects, while improving the diffraction efficiency of structured light and reducing uniformity errors.

[0149] Fourth, solve the problem of large size and complex structure of traditional optical systems.

[0150] Traditional diffractive optical elements require the addition of collimating lenses, which significantly increases the size and complexity of the system. This embodiment eliminates the need for additional collimating lenses by designing a metasurface that integrates collimation and beam splitting, achieving a more compact optical system design and significantly reducing system size.

[0151] The present application also provides a metasurface design device, such as Figure 11 As shown, the metasurface design device includes:

[0152] The position matching module 111 is configured to introduce a grating structure on the basis of the GS algorithm to obtain a GS algorithm model based on the grating diffraction order, and use the GS algorithm model based on the grating diffraction order to obtain the sampling point position of the target surface;

[0153] A database construction module 112 is configured to construct a multi-angle structure database under a complex light field;

[0154] The iterative design module 113 is configured to perform reverse design of the metasurface characteristics based on the sampling point positions of the target surface and the multi-angle structure database under the complex light field to obtain the metasurface structure.

[0155] In some embodiments, the location matching module is further configured to:

[0156] The sampling point coordinates of the DOE surface are represented by (m0, n0), and the total number of sampling points on the DOE surface is M*N; where m0 and n0 are the m0th row and n0th column of the discrete phase within a single grating period, and M and N are the M and N values ​​of the phase discrete within the horizontal axis and the vertical axis within a single grating period, respectively.

[0157] The sampling point coordinates of the image plane are represented by (m, n), and the total number of sampling points in the image plane is M*N; where m and n are the diffraction orders in two directions of the two-dimensional grating when the plane light is normally incident.

[0158] In some embodiments, the database construction module is further configured to:

[0159] The relationship between the structural parameters and the modulation phase is described based on the following functional relationship:

[0160] φ i =f i (R)

[0161] Where R is the elementary structure parameter; i is the i-th diffraction order; φ irepresents the modulation phase corresponding to the elementary structure parameters under the i-th diffraction order;

[0162] According to the functional relationship, the mapping relationship between the nanorods and the phase at different incident angles is obtained; and based on the mapping relationship between the nanorods and the phase at different incident angles, a multi-angle structure database under complex light fields is constructed.

[0163] In some embodiments, the iterative design module is further configured to:

[0164] The target amplitude is combined with a random phase symmetric about the x-axis and y-axis to form a complex amplitude u' on the image plane. i ;

[0165] The complex amplitude is processed by inverse Fourier transform to generate the complex amplitude of the DOE surface;

[0166] Based on the phase information extracted from the complex amplitude of the DOE surface, the DOE phase information is restored through the correspondence between the nanopillars and the phase under normal incidence. The structural parameters of the metasurface are obtained; where R(m0,n0) represents the parameters related to the nanopillar and the phase, and φ(m0,n0) represents the discrete phase of the m0th row and n0th column. It represents the correspondence between the phase of a plane wave and the parameters of the nanopillars when the plane wave is incident normally. It is part of the multi-angle structure database under complex light fields.

[0167] Using φ i '(m0,n0)=f i (R(m0,n0)) calculates the phase modulation effect of the metasurface at different incident angles and superimposes the phase factor ψ caused by the oblique incidence of plane light i , and the total phase φ of the diffraction surface is obtained i ", the calculation formula is:

[0168]

[0169] Among them, φ i ' is the phase modulation produced by the metasurface when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence, L x is the horizontal axis length of a single grating period, L y is the ordinate length of a single grating period;

[0170] The complex amplitude of the diffraction surface can be expressed as exp(iφ i ”(m0,n0)), by Fourier transforming the complex amplitude, we can get the complex amplitude distribution u of each diffraction order in the far field. i ”(m0,n0), the calculation formula is:

[0171] ui ”(m0,n0)=FFT(exp(iφ i ”(m0,n0)))

[0172] Where, FFT represents Fourier transform, exp represents exponential function;

[0173] The objective function is constructed with the goal of optimizing the matching degree between the far-field diffraction order amplitude and the target diffraction order amplitude at different incident angles:

[0174] FoM i (m,n)=(u i ”(m,n)-A Ti (m,n)) 2

[0175] Where A Ti (m,n) is the target amplitude distribution when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence, FoM i (m,n) is the value of the objective function when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence, u” i (m,n) is the complex amplitude distribution of each diffraction order in the far field after being modulated by the metasurface when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence;

[0176] The DOE surface phase φ is calculated by the objective function i "The derivative of the phase gradient is obtained, and the gradient expression of the objective function with respect to the DOE surface phase is:

[0177]

[0178] Where, Indicates u" i conjugation, Indicates A Ti The conjugate of (m,n), real means taking the real part, and conj means taking the conjugate;

[0179] According to the relationship between phase and nanorod geometric parameters φ = f i (R), the gradient of the objective function value with respect to the nanopillar radius is calculated by the following formula:

[0180]

[0181] Using the gradient of the objective function value with respect to the nanopillar radius, the nanopillar radius R(m0,n0) is updated using the maximum-minimum method in each iteration. The update formula is:

[0182]

[0183] Where k is the gradient learning rate factor, and max is the maximum value function;

[0184] After obtaining the preliminary optimized metasurface parameters, the phase modulation of the metasurface is obtained by the formula φ(m0,n0)=f0(R(m0,n0)) under normal incidence; the amplitude A0(m0,n0)=1 is set, and the complex amplitude distribution of each diffraction order in the image plane is obtained by Fourier transform. In each iteration, the phase part of the obtained complex amplitude of each diffraction order in the image plane is retained, and the amplitude part is replaced by the target complex amplitude and multiplied by the amplitude correction factor e. This process is repeated until the predetermined number of iterations is reached or the diffraction efficiency and uniformity of the target diffraction order meet the design requirements, and the iteration is stopped to obtain the final metasurface structure.

[0185] In some embodiments, the apparatus further comprises a collimating beam splitting module, wherein the collimating beam splitting module is further configured to:

[0186] The grating phase and the collimation phase are superimposed to obtain a phase that realizes the integration of collimation and beam splitting at the same time; wherein the expression of the collimation phase is:

[0187]

[0188] Where, Collimating Phase is the collimation phase, λ is the wavelength, r imn is the distance between the phase of the mth row and nth column of the DOE surface and the origin of the DOE surface, and f is the effective focal length, which is expressed as:

[0189]

[0190] Where L1 is the distance between the VCSELs array and the metasurface, L2 is the thickness of the metasurface substrate, and n is the refractive index of the substrate.

[0191] Phase and function that will simultaneously realize the integration of collimation and beam splitting By correspondingly performing the above steps, we obtain a metasurface that realizes the integration of collimation and beam splitting at the same time.

[0192] In some embodiments, the device further includes a layer film design module, which is further configured to design a protective layer and an anti-reflection film; wherein the thickness corresponding to the best diffraction efficiency and uniformity within a single period is used as the thickness of the protective layer; the anti-reflection film includes a first anti-reflection film and a second anti-reflection film connected, the refractive index of the second anti-reflection film is higher than the refractive index of the protective layer, and the refractive index of the first anti-reflection film is lower than the refractive index of the protective layer.

[0193] An embodiment of the present application provides an electronic device, which may include a processor and a memory, wherein the processor and the memory can communicate with each other; illustratively, the processor and the memory communicate with each other via a communication bus.

[0194] The processor executes the computer-executable instructions stored in the memory, so that the processor implements the solutions in the above embodiments. The processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0195] The communication bus can be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus, among others. System buses can be divided into address buses, data buses, and control buses. For ease of illustration, the figure shows only one thick line, but this does not imply that there is only one bus or type of bus. Transceivers are used to enable communication between the database access device and other computers (e.g., clients, read-write libraries, and read-only libraries). Memory may include random access memory (RAM) and may also include non-volatile memory.

[0196] The electronic device provided in the embodiment of the present application may be the terminal device of the above embodiment.

[0197] An embodiment of the present application further provides a computer-readable storage medium, in which computer instructions are stored. When the computer instructions are executed on a computer, the computer executes the technical solution of the metasurface design method of the above embodiment.

[0198] An embodiment of the present application also provides a computer program product, which includes a computer program stored in a computer-readable storage medium. At least one processor can read the computer program from the computer-readable storage medium, and when the at least one processor executes the computer program, it can implement the technical solution of the metasurface design method in the above embodiment.

[0199] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of modules is only a logical function division. In actual implementation, there may be other division methods, such as multiple modules can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interface, device or module, which can be electrical, mechanical or other forms.

[0200] Modules described as separate components may or may not be physically separate, and components shown as modules may or may not be physical units, that is, they may be located in one place or distributed across multiple network elements. Some or all of these modules may be selected to implement the solution of this embodiment based on actual needs.

[0201] In addition, the functional modules in the various embodiments of the present application may be integrated into a single processing unit, or each module may exist physically separately, or two or more modules may be integrated into a single unit. The above-mentioned modules may be implemented in the form of hardware or hardware plus software functional units.

[0202] The above-mentioned integrated module implemented in the form of a software functional module can be stored in a computer-readable storage medium. The above-mentioned software functional module is stored in a storage medium and includes a number of instructions for causing a computer device (which can be a personal computer, server, or network device, etc.) or a processor to perform some steps of the methods of various embodiments of the present application.

[0203] It should be understood that the processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), or application-specific integrated circuits (ASICs). A general-purpose processor may be a microprocessor or any conventional processor. The steps of the method disclosed in the present invention may be directly implemented by a hardware processor or implemented by a combination of hardware and software modules in the processor.

[0204] The memory may include a high-speed RAM memory, and may also include non-volatile storage NVM, such as at least one disk memory, and may also be a USB flash drive, a mobile hard disk, a read-only memory, a magnetic disk or an optical disk.

[0205] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus. Buses can be classified into address buses, data buses, and control buses. For ease of illustration, the buses in the drawings of this application are not limited to just one bus or just one type of bus.

[0206] The storage medium may be implemented by any type of volatile or non-volatile memory device, or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The storage medium may be any available medium that can be accessed by a general-purpose or special-purpose computer.

[0207] An exemplary storage medium is coupled to a processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be an integral part of the processor. The processor and the storage medium can be located in an application specific integrated circuit (ASIC). Of course, the processor and the storage medium can also exist as discrete components in an electronic control unit or a main control device.

[0208] Those skilled in the art will appreciate that all or part of the steps in the above-described method embodiments can be implemented using hardware associated with program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0209] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A metasurface design method, characterized in that: The method comprises: On the basis of GS algorithm, a grating structure is introduced to obtain a GS algorithm model based on grating diffraction orders, and the sampling point position of the target surface is obtained by using the GS algorithm model based on grating diffraction orders; Construct a multi-angle structure database under complex light fields; Based on the sampling point positions of the target surface and the multi-angle structure database under the complex light field, reverse design of the metasurface characteristics is performed to obtain the metasurface structure; The sampling point positions of the target surface include the sampling point coordinates of the DOE surface and the sampling point coordinates of the image plane. The sampling point positions of the target surface are obtained using the GS algorithm model based on the grating diffraction order, including: The sampling point coordinates of the DOE surface are expressed as ( m 0, n 0) indicates that the total number of sampling points on the DOE surface is M * N ;in, m 0 and n 0 are the discrete phases within a single grating period. m Line 0 n 0 columns, M and N The phase in the horizontal axis is discrete into M values ​​and the phase in the vertical axis is discrete into N values ​​within a single grating period; The sampling point coordinates of the image plane are expressed as ( m , n ) indicates that the total number of sampling points on the image plane is M * N ;in m and n They are the diffraction orders in two directions of the two-dimensional grating when plane light is incident normally; Construct a multi-angle structure database under complex light fields, including: The relationship between the structural parameters and the modulation phase is described based on the following functional relationship: ； Where R is the basic structural parameter; i For the i diffraction orders; Indicates the i The modulation phase corresponding to the elementary structure parameters under the diffraction order; According to the functional relationship, the mapping relationship between the nanorods and the phase at different incident angles is obtained; and based on the mapping relationship between the nanorods and the phase at different incident angles, a multi-angle structure database under complex light fields is constructed.

2. The metasurface design method according to claim 1, wherein: Based on the sampling point positions of the target surface and the multi-angle structure database under complex light fields, reverse design of the metasurface characteristics is performed to obtain the metasurface structure, including: The target amplitude is related to x Axis and y Axisymmetric random phase synthesis into complex amplitude in the image plane ; The complex amplitude is processed by inverse Fourier transform to generate the complex amplitude of the DOE surface; Based on the phase information extracted from the complex amplitude of the DOE surface, the DOE phase information is restored through the correspondence between the nanorods and the phase under normal incidence. The structural parameters of the metasurface are obtained; among them, R ( m 0, n 0) represents the parameters related to the nanopillar and phase, Indicates the m Line 0 n The discrete phase of column 0, represents the correspondence between the phase and the parameters of the nanopillar when the plane wave is incident normally; use Calculate the phase modulation effect of the metasurface at different incident angles and superimpose the phase factor caused by oblique incident plane light , and the total phase of the diffraction surface is obtained , the calculation formula is: ； in, is the phase modulation produced by the metasurface when the plane wave incident angle is equal to the i-th order diffraction angle at normal incidence, L x is the abscissa length of a single grating period, L y is the ordinate length of a single grating period; The complex amplitude of the diffraction surface can be expressed as By performing Fourier transform on the complex amplitude, the complex amplitude distribution of each diffraction order in the far field is obtained. , the calculation formula is: ； Where, FFT represents Fourier transform, exp represents exponential function; The objective function is constructed with the goal of optimizing the matching degree between the far-field diffraction order amplitude and the target diffraction order amplitude at different incident angles: ； Where, is the target amplitude distribution when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence, is the value of the objective function when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence, is the complex amplitude distribution of each diffraction order in the far field after being modulated by the metasurface when the plane wave incident angle is equal to the diffraction angle of the i-th order at normal incidence; DOE surface phase is calculated by objective function The derivative of , the corresponding phase gradient is obtained. The gradient expression of the objective function with respect to the DOE surface phase is: ； Where, express conjugation, express The conjugate of , real means taking the real part, conj means taking the conjugate; According to the relationship between phase and nanorod geometric parameters , the gradient of the objective function value with respect to the nanopillar radius is calculated by the following formula: ； Using the gradient of the objective function value to the nanopillar radius, the nanopillar radius is updated using the maximum and minimum method in each iteration. , the update formula is: ； Where, k is the gradient learning rate factor, and max is the maximum value function; After obtaining the preliminary optimized metasurface parameters, the formula under normal incidence is used Get the phase modulation of the metasurface; set the amplitude The complex amplitude distribution of each diffraction order in the image plane is obtained by Fourier transform. In each iteration, the phase part of the complex amplitude of each diffraction order in the image plane is retained, and the amplitude part is replaced by the target complex amplitude and multiplied by the amplitude correction factor. e , and this process is repeated until the predetermined number of iterations is reached or the diffraction efficiency and uniformity of the target diffraction order meet the design requirements, and the iteration is stopped to obtain the final metasurface structure.

3. The metasurface design method according to claim 2, wherein: After performing reverse design of metasurface characteristics based on the sampling point positions of the target surface and a multi-angle structure database under a complex light field to obtain the metasurface structure, the method further includes: The grating phase and the collimation phase are superimposed to obtain a phase that realizes the integration of collimation and beam splitting at the same time; wherein the expression of the collimation phase is: ； Where, Collimating Phase is the collimation phase, is the wavelength, r imn is the distance between the phase of the mth row and nth column of the DOE surface and the origin of the DOE surface, is the effective focal length, expressed as: ； Where, L 1 is the distance from the VCSELs array to the metasurface, L 2 is the base thickness of the metasurface, n is the refractive index of the substrate; Phase and function that will simultaneously realize the integration of collimation and beam splitting By correspondingly performing the above steps, we obtain a metasurface that realizes the integration of collimation and beam splitting at the same time.

4. The metasurface design method according to claim 2, wherein: After reverse engineering the metasurface characteristics based on the sampling point positions of the target surface and a database of multi-angle structures under complex light fields to obtain the metasurface structure, the method further includes designing a protective layer and an anti-reflection film; wherein the thickness of the protective layer is determined by the thickness corresponding to the optimal diffraction efficiency and uniformity within a single period; and the anti-reflection film includes a first anti-reflection film and a second anti-reflection film connected to each other, the refractive index of the second anti-reflection film being higher than the refractive index of the protective layer, and the refractive index of the first anti-reflection film being lower than the refractive index of the protective layer.

5. A metasurface design device, based on the method according to any one of claims 1 to 4, characterized in that: The device comprises: The position matching module is configured to introduce a grating structure on the basis of the GS algorithm to obtain a GS algorithm model based on the grating diffraction order, and use the GS algorithm model based on the grating diffraction order to obtain the sampling point position of the target surface; A database construction module is configured to construct a multi-angle structure database under a complex light field; The iterative design module is configured to perform reverse design of the metasurface characteristics based on the sampling point positions of the target surface and a multi-angle structure database under a complex light field to obtain the metasurface structure.

6. An electronic device, characterized in that: include: a processor, and a memory communicatively connected to the processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the metasurface design method according to any one of claims 1 to 4.

7. A computer-readable storage medium, characterized in that The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the metasurface design method according to any one of claims 1 to 4.

8. A computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the computer program implements the metasurface design method according to any one of claims 1 to 4.

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