A multi-channel information encryption display device based on metasurface and a design method thereof

Abstract

The application belongs to the technical field of micro-nano optics, and discloses a multi-channel information encryption display device based on a metasurface and a design method thereof. The multi-channel information encryption display device is designed based on the metasurface. Linearly polarized light is incident to the device, and a first image is displayed after passing through a polarizer. The transmission axis directions of the polarizer and the analyzer are kept unchanged. The device is rotated by a first angle, and a second image is displayed. Encryption image design wavelength and design polarization state information are obtained. Coherent light with the design wavelength and the design polarization state is incident to the device. A third image can be observed in a Fraunhofer diffraction zone, and encryption image design distance information is obtained. Coherent light with the design wavelength and the design polarization state is incident. A fourth image can be observed at the design distance. The image multiplexing display technology of the metasurface can solve the problem of low security of the image display scheme based on the metasurface in the prior art, and can improve the security of information.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano optics technology, and more specifically, relates to a multi-channel information encryption display device based on metasurface and its design method. Background Technology

[0002] Metasurfaces are a new type of micro- and nano-optical device that enables efficient manipulation and control of light waves. They are surfaces composed of precisely manufactured two-dimensional or three-dimensional microstructures with dimensions comparable to the wavelength of light, thus allowing for precise control of light.

[0003] Metasurface image display utilizes the local phase control and reflection properties of metasurfaces. By designing and manipulating the shape and size of microstructures on the metasurface, light can be controlled to generate images with specific shapes and brightness distributions. By using the same metasurface to modulate different light waves in different ways, multiple image display methods can be reused. Some of these image display methods can only be observed under specific conditions, thus enabling encrypted image display.

[0004] Although a large number of studies have been conducted on metasurfaces to achieve high-quality image display, most of the images are directly observable, making the displayed information easy to be stolen. Summary of the Invention

[0005] This invention addresses the problem of low security in existing metasurface-based image display solutions by providing a multi-channel information encryption display device based on metasurfaces and its design method.

[0006] This invention provides a design method for a multi-channel information encryption display device based on metasurfaces, comprising the following steps:

[0007] Step 1: Construct the basic structure of a multi-channel information encryption display device based on a metasurface. The basic structure includes a substrate and a nanobrick array on the substrate. The substrate is divided into multiple unit structures of the same size. The nanobrick array includes several nanobricks with the same size parameters. Each unit structure and one nanobrick on its working surface constitute a nanobrick structure unit. The size parameters of the nanobrick structure unit are optimized so that the function of the nanobrick structure unit is equivalent to a micro / nano half-wave plate when the design wavelength is perpendicularly incident.

[0008] Step 2, a linearly polarized light with intensity I0, polarization direction α1 and design wavelength is formed by a polarizer, and the linearly polarized light is perpendicularly incident on the nano-brick structure unit and then passes through an analyzer with an analyzing direction α2, to obtain a first function relationship between a first exit light intensity I1 and the polarization direction α1 of the linearly polarized light, the turning angle θ of the nano-brick in the nano-brick structure unit, and the analyzing direction α2 of the analyzer; a first image is designed, the first image is a gray image without containing encryption information, and four alternative values of the turning angle θ of the nano-brick in each nano-brick structure unit are calculated according to the gray distribution of the first image and the first function relationship;

[0009] Step 3, the transmission axis directions of the polarizer and the analyzer are kept unchanged, the nano-brick structure unit is rotated by a first angle, to obtain a second function relationship between a second exit light intensity I2 and the polarization direction α1 of the linearly polarized light, the turning angle θ of the nano-brick in the nano-brick structure unit, and the analyzing direction α2 of the analyzer; a second image is designed, the second image is an image containing encryption image design wavelength and design polarization state information; two alternative values are selected from the four alternative values of the turning angle θ of the nano-brick according to the intensity distribution of the second image and the second function relationship;

[0010] Step 4, a third image and a fourth image are designed, the third image is an image containing encryption image design distance information, and the fourth image is an encryption image; a final value is determined from the multiple alternative values of the turning angle θ of the nano-brick in each nano-brick structure unit by using a simulated annealing algorithm; the nano-brick array is arranged according to the determined turning angle θ of the nano-brick, to obtain a super surface-based multi-channel information encryption display device;

[0011] The first image is displayed by the super surface-based multi-channel information encryption display device when a linearly polarized light with intensity I0, polarization direction α1 and design wavelength is incident on the super surface-based multi-channel information encryption display device and then passes through an analyzer with polarization direction α2; the second image is displayed by the super surface-based multi-channel information encryption display device when the transmission axis directions of the polarizer and the analyzer are kept unchanged and the super surface-based multi-channel information encryption display device is rotated by the first angle, and encryption image design wavelength and design polarization state information are obtained; the third image is observed in a Fraunhofer diffraction zone and encryption image design distance information is obtained when a coherent light wave with design wavelength and design polarization state is incident on the super surface-based multi-channel information encryption display device; and the fourth image is observed at a design distance when a coherent light with design wavelength and design polarization state is incident.

[0012] Preferably, the size parameters include a long axis L, a short axis W, and a height H of the nano-brick, and a side length C of a working surface of the unit structure; the long axis L and the short axis W are not equal; an xoy coordinate system is established with two edges parallel to the working surface as the x-axis and the y-axis respectively, and a turning angle θ of the nano-brick is an included angle between the long axis L of the nano-brick and the x-axis.

[0013] Preferably, the first function relationship is expressed as: I'1 = cos 2 (2θ-α2-α1); wherein I'1 represents a normalized intensity of the first emergent light I1; the second function relationship is expressed as: wherein I'2 represents a normalized intensity of the second emergent light I2, represents the first angle.

[0014] Preferably, when the direction of the pass axis of the polarizer is perpendicular to the direction of the pass axis of the analyzer, α2 = α1 + π / 2, and the first angle is π / 8, the first function relationship is expressed as: I'1 = cos 2 (2θ-2α2-π / 2); and the second function relationship is expressed as: I'2 = cos 2 (2θ-2α2-3π / 4).

[0015] Preferably, when α1 = -π / 4 and α2 = π / 4, I'1 = cos 2 (2θ), and I'2 = cos 2 (2θ-π / 4).

[0016] Preferably, the second image is a binary image.

[0017] Preferably, four alternative values of the turning angle θ of the nano-brick satisfy: θ0 is a first alternative angle.

[0018] Preferably, an evaluation function used when using the simulated annealing algorithm is:

[0019]

[0020] wherein cost is the evaluation function, M1 and N1 are respectively a row and a column pixel number of the first image; I3 is an intensity distribution of light in a Fraunhofer diffraction zone when a design wavelength is incident; Img3 is an intensity distribution of the third image; I4 is an intensity distribution of light in a Fresnel diffraction zone at a design distance when the design wavelength is incident; and Img4 is an intensity distribution of the fourth image.

[0021] Preferably, the number of pixels of the first image is M1*N1, the number of pixels of the second image is M2*N2, and M2 < M1, N2 < N1 are satisfied; according to the intensity distribution of the second image and the second functional relationship, for each of the nanobrick structural units within the display area of the second image, two alternative values are selected from the four alternative values of the rotation angle θ of the nanobrick; for each of the nanobrick structural units outside the display area of the second image, the four alternative values of the rotation angle θ of the nanobrick are retained; the display area of the second image is the area for displaying an image containing the encrypted image design wavelength and design polarization state information.

[0022] On the other hand, the present invention provides a multi-channel information encryption display device based on a metasurface, which is prepared by using the design method of the multi-channel information encryption display device based on a metasurface described above.

[0023] One or more technical solutions provided in the present invention have at least the following technical effects or advantages:

[0024] The present invention designs a multi-channel information encryption display device based on a metasurface. A linearly polarized light designed is incident on the device and after passing through an analyzer, a first image (a grayscale image without encrypted information) is displayed; keeping the transmission axis directions of the polarizer and the analyzer unchanged, after rotating the multi-channel information encryption display device based on a metasurface by a first angle, a second image (an image containing the encrypted image design wavelength and design polarization state information) is displayed. Therefore, the encrypted image design wavelength and design polarization state information can be obtained; a coherent light wave with a designed wavelength and design polarization state is incident on the multi-channel information encryption display device based on a metasurface, and a third image (an image containing the encrypted image design distance information) can be observed in the Fraunhofer diffraction region. Therefore, the encrypted image design distance information can be obtained; with a coherent light with a designed wavelength and design polarization state incident, a fourth image can be observed at the designed distance. That is, the present invention enables the encrypted information and the secret key to be stored in the same metasurface by using the image multiplexing display technology of the metasurface, and can be read and displayed in different ways. The present invention can not only improve the security of information, but also improve the information storage density, and the device has a compact structure and a high tolerance to processing errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of a multi-channel information encryption display implemented by a multi-channel information encryption display device based on a metasurface provided in an embodiment of the present invention;

[0026] Figure 2 is a schematic structural diagram of a nanobrick structural unit in a multi-channel information encryption display device based on a metasurface provided in an embodiment of the present invention;

[0027] Figure 3This is a schematic diagram of the structure of a multi-channel information encryption display device based on metasurface provided in an embodiment of the present invention;

[0028] Figure 4 This is a top view of a multi-channel information encryption display device based on a metasurface provided in an embodiment of the present invention;

[0029] Figure 5 This is the transmission response curve of the optimized nanobrick structure unit in the embodiment of the present invention;

[0030] Figure 6 This is the first image designed in the embodiments of the present invention;

[0031] Figure 7 This is the fourth image designed in the embodiments of the present invention;

[0032] Figure 8 This is the second image designed in the embodiments of the present invention;

[0033] Figure 9 This is the third image designed in the embodiments of the present invention;

[0034] Figure 10 This is a distribution diagram of the turning angle of the nanobricks designed in the embodiments of the present invention;

[0035] Figure 11 This is the display result of the optimized first image in the embodiment of the present invention;

[0036] Figure 12 This is the optimized display result of the second image in this embodiment of the invention;

[0037] Figure 13 This is the optimized display result of the third image in the embodiment of the present invention;

[0038] Figure 14 This is the display result of the optimized fourth image in this embodiment of the invention. Detailed Implementation

[0039] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0040] Example 1:

[0041] Example 1 provides a design method for a multi-channel information encryption display device based on metasurfaces, including the following steps:

[0042] Step 1: Construct the basic structure of a multi-channel information encryption display device based on a metasurface. The basic structure includes a substrate and a nanobrick array on the substrate. The substrate is divided into multiple unit structures of the same size. The nanobrick array includes several nanobricks with the same size parameters. Each unit structure and one nanobrick on its working surface constitute a nanobrick structure unit. The size parameters of the nanobrick structure unit are optimized so that the function of the nanobrick structure unit is equivalent to a micro / nano half-wave plate when the design wavelength is perpendicularly incident.

[0043] The dimensional parameters include the major axis L, minor axis W, and height H of the nanobrick, as well as the side length C of the working surface of the unit structure; the major axis L and minor axis W are not equal; an xoy coordinate system is established with the directions parallel to the two sides of the working surface as the x-axis and y-axis, respectively, and the turning angle θ of the nanobrick is the angle between the major axis L of the nanobrick and the x-axis.

[0044] Step 2: Using a polarizer, linearly polarized light with intensity I0, polarization direction α1, and a designed wavelength is generated. This linearly polarized light is incident perpendicularly onto the nanobrick structure unit and then passes through an analyzer with polarization direction α2. A first functional relationship is obtained between the first emitted light intensity I1, the polarization direction α1 of the linearly polarized light, the turning angle θ of the nanobrick in the nanobrick structure unit, and the polarization direction α2 of the analyzer. A first image is designed, which is a grayscale image without encrypted information. Based on the grayscale distribution of the first image and the first functional relationship, four alternative values ​​for the turning angle θ of the nanobrick in each nanobrick structure unit are calculated.

[0045] The first functional relationship is expressed as: I1′=cos 2 (2θ-α2-α1); where I1′ represents the normalized intensity of the first emitted light intensity I1.

[0046] The four alternative values ​​for the turning angle θ of the nanobrick satisfy the following: θ0 is the first alternative angle.

[0047] Step 3: Keeping the transmission axis directions of the polarizer and the analyzer unchanged, rotate the nanobrick structure unit by a first angle to obtain a second functional relationship between the second emitted light intensity I2 and the polarization direction α1 of the linearly polarized light, the turning angle θ of the nanobrick in the nanobrick structure unit, and the polarization direction α2 of the analyzer; design a second image, which is an image containing the design wavelength and design polarization state information of the encrypted image; based on the intensity distribution of the second image and the second functional relationship, select two candidate values ​​from the four candidate values ​​of the turning angle θ of the nanobrick.

[0048] Among them, the second functional relationship is expressed as: In the formula, I′2 represents the normalized intensity of the second output light intensity I2, represents the first angle.

[0049] The second image is a binary image.

[0050] Specifically, the number of pixels of the first image is M1*N1, the number of pixels of the second image is M2*N2, and M2<M1, N2<N1 are satisfied; according to the intensity distribution of the second image and the second functional relationship, for each of the nanobrick structural units within the display area of the second image, two alternative values are selected from the four alternative values of the turning angle θ of the nanobrick; for each of the nanobrick structural units outside the display area of the second image, the four alternative values of the turning angle θ of the nanobrick are retained; the display area of the second image is the area for displaying an image containing the encrypted image design wavelength and design polarization state information.

[0051] Step 4: Design a third image and a fourth image. The third image is an image containing encrypted image design distance information, and the fourth image is an encrypted image; using the simulated annealing algorithm, determine the final value from the multiple alternative values of the turning angle θ of the nanobrick in each of the nanobrick structural units; arrange the nanobrick array according to the determined turning angle θ of the nanobrick to obtain a multi-channel information encryption display device based on a metasurface.

[0052] Among them, the evaluation function used when using the simulated annealing algorithm is:

[0053]

[0054] In the formula, cost is the evaluation function, M1 and N1 are the number of row and column pixels of the first image respectively; I3 is the light intensity distribution in the Fraunhofer diffraction region when incident with the design wavelength; Img3 is the intensity distribution of the third image; I4 is the light intensity distribution at the design distance in the Fresnel diffraction region when incident with the design wavelength; Img4 is the intensity distribution of the fourth image.

[0055] See Figure 1A linearly polarized light with intensity I0, polarization direction α1, and designed wavelength is generated using a polarizer. Incident light wave 1 is incident on the metasurface-based multi-channel information encryption display device 2 and, after passing through an analyzer with polarization direction α2, displays the first image 3. The transmission axis direction 6 of the polarizer is perpendicular to the transmission axis direction 7 of the analyzer. Keeping the transmission axis directions of the polarizer and analyzer unchanged, the metasurface-based multi-channel information encryption display device 2 is rotated by the first angle to display the second image, obtaining the encrypted image's designed wavelength and designed polarization state information. A coherent light wave with the designed wavelength and designed polarization state is incident on the metasurface-based multi-channel information encryption display device 2, and the third image 5 can be observed in the Fraunhofer diffraction region, obtaining the encrypted image's designed distance information. A coherent light wave with the designed wavelength and designed polarization state is incident on the device, and the fourth image 4 can be observed at the designed distance.

[0056] See Figure 2 , Figure 3 , Figure 4 The nanobrick structure unit includes a working surface 202 and nanobricks 201 disposed on the working surface 202. The working surface 202 is made of SiO2 material, and the nanobricks 201 are made of Si material. An xoy coordinate system is established with the two directions parallel to the working surface 202 as the x-axis and y-axis, respectively. The nanobrick 201 has a major axis L and a minor axis W on a surface parallel to the working surface 202. The turning angle θ of the nanobrick is the angle between the major axis L and the x-axis. The optimized dimensions of the nanobrick structure unit are: side length C of the working surface = 300 nm, height H of the nanobrick = 360 nm, major axis L of the nanobrick = 155 nm, and minor axis W of the nanobrick = 60 nm. The transmission response of the nanobrick structure unit with the corresponding dimensional parameters is obtained through simulation as follows: Figure 5 As shown, the function of the nano-brick structure unit with a design wavelength of λ = 633 nm is equivalent to a micro / nano half-wave plate.

[0057] The present invention will now be further described.

[0058] The working principle involved in step 2 above is as follows:

[0059] The nanobrick unit structure can be described using the same Jones matrix. The Jones matrix G(θ) of the optimized anisotropic nanobrick unit structure at a turning angle θ can be expressed as:

[0060]

[0061] Where R is the rotation matrix, G0 is the Jones matrix of the nanobrick structural unit along the x-axis, θ is the angle between the direction of the nanobrick's long axis and the x-axis, and A and B are the complex reflection (or transmission) coefficients along the long and short axes of the nanobrick, respectively.

[0062] When linearly polarized light passes through an anisotropic nanobrick unit structure and then through an analyzer, the Jones vector of the transmitted light wave is expressed as:

[0063]

[0064] In the formula, α1 is the angle between the vibration direction of the incident linearly polarized light and the x-axis, and α2 is the angle between the transmission axis of the analyzer and the x-axis.

[0065] When the intensity of the incident linearly polarized light is I0, the intensity I1 of the light emitted after passing through the anisotropic nanobrick unit structure and then through the analyzer is:

[0066]

[0067] When the nanobrick unit structure exhibits anisotropy, A≠B, and when the transmission axis of the polarizer is perpendicular to the transmission axis of the analyzer, i.e., α2=α1+π / 2:

[0068]

[0069] When the nanobrick unit structure functions as a micro / nano half-wave plate, A = 1, B = -1. Therefore, equation (4) can be simplified to:

[0070] I1=I0cos 2 (2θ-2α²-π / 2) (5)

[0071] The normalized intensity I′1 of the emitted light intensity I1 is:

[0072] I′1=cos 2 (2θ-2α²-π / 2) (6)

[0073] Specifically, taking α1 = -π / 4 and α2 = π / 4, equation (5) can be expressed as:

[0074] I1=I0cos 2 (2θ)

[0075] Equation (6) is expressed as:

[0076] I′1=cos 2 (2θ)

[0077] Due to the periodicity and symmetry of the cosine function, for each specific intensity distribution, there are four specific θ values ​​corresponding to it, and the four optional turning angles satisfy the following:

[0078]

[0079] If the nanobrick unit structure is rotated along its optical axis And if the transmission axis directions of the polarizer and analyzer remain unchanged, then at this time:

[0080]

[0081] When the rotation angle hour:

[0082]

[0083] When the nanobrick unit structure functions as a micro / nano half-wave plate, A = 1, B = -1, and equation (9) can be simplified to:

[0084] I2=I0cos 2 (2θ-2α²-3π / 4) (10)

[0085] The normalized intensity I′2 corresponding to the emitted light intensity I2 is:

[0086] I′2=cos 2 (2θ-2α²-3π / 4) (11)

[0087] Specifically, taking α1 = -π / 4 and α2 = π / 4, equation (10) can be expressed as:

[0088] I2=I0cos 2 (2θ-π / 4)

[0089] Equation (11) is expressed as:

[0090] I′2=cos 2 (2θ-π / 4)

[0091] For a binary image, two possible values ​​are determined based on the 0 or 1 value of each pixel. Specifically: if the pixel value is 0, then... Then the two possible values ​​at this pixel are Conversely, it is If the pixel value at that location is 1, Then the two possible values ​​at this pixel are Conversely, it is The nanobrick turning angle θ in each nanobrick structural unit outside the display area of ​​the binary image Img2 retains four selectable values.

[0092] choose Figure 6The grayscale image Img1 (i.e., the first image) to be displayed has a pixel count of 1000*1000. Select... Figure 7 For the image Img4 (the fourth image) that needs to be encrypted, the encryption wavelength is 633nm, the polarization state is set to RCP (right-hand circularly polarized light), and the encryption distance is 600μm. Therefore, the binary image Img2 (the second image) and image Img3 (the third image) are designed as follows: Figure 8 and Figure 9 As shown. Among them. Figure 8 The pixel count is 300*300. According to... Figure 6 grayscale distribution and Figure 8 The intensity distribution can determine alternative values ​​for the turning angle of the nanobricks in each nanobrick structural unit.

[0093] The working principle involved in step 4 above is as follows:

[0094] In the Fraunhofer diffraction region, after adopting the Fraunhofer approximation, the diffraction formula for light waves is:

[0095]

[0096] In the Fresnel diffraction region, the Fresnel diffraction formula expresses the incident light field as the amplitude and phase of the wavefront, and then calculates the new wavefront amplitude and phase over the propagation distance by integration, specifically:

[0097]

[0098] For a design wavelength λ, with a steering angle distribution of θ for the nanobrick array, the complex amplitude modulation of the outgoing cross-polarized circularly polarized light when incident on circularly polarized light is:

[0099]

[0100] When the nanobrick unit structure functions as a micro / nano half-wave plate, A = 1, B = -1, and equation (14) can be simplified to:

[0101]

[0102] Where σ=1 and σ=-1 represent that the polarization state of the light wave is left-handed circularly polarized light or right-handed circularly polarized light, respectively.

[0103] In the Fraunhofer diffraction region, the intensity distributions corresponding to the designed wavelengths are as follows:

[0104]

[0105] For the Fresnel diffraction region design distance z1, the light intensity distribution corresponding to the design wavelength is as follows:

[0106]

[0107] It is evident that Fourier holography is independent of the observation plane position, and due to the properties of the Fourier transform, circularly polarized light with different rotation directions exhibits a centrally symmetrical intensity distribution. Therefore, different polarized light incident at different distances can display corresponding images, and the same intensity distribution can be observed at different distances in the Fraunhofer diffraction region, differing only in scale. In contrast, the intensity distribution observed by Fresnel diffraction is related to the incident light wavelength, the observation distance, and the initial complex amplitude distribution. Therefore, the designed Fresnel hologram can only be observed with light of a specific wavelength and at a specific polarization state at a specific distance.

[0108] A simulated annealing algorithm is used to optimize and select the optimal result from the candidate values ​​of the turning angle of the nanobricks in the nanobrick structural units at each location. This ensures that, at the design wavelength λ, when coherent light of the corresponding polarization state is incident, the target image Img3 and the image Img4 to be encrypted are displayed at a specified distance in the Fresnel diffraction region and in the Fraunhofer diffraction region, respectively. The evaluation function for the simulated annealing algorithm optimization is:

[0109]

[0110] The optimized distribution of the turning angle θ of the nanobrick array is as follows: Figure 10 As shown.

[0111] According to the formula I′1=cos 2 (2θ) The grayscale image corresponding to the optimized steering angle distribution is obtained as follows: Figure 11 As shown; according to the formula I′2=cos 2 (2θ-π / 4) yields the image of the metasurface after rotating by a specific angle, as shown below. Figure 12 As shown; according to formula (17), the intensity distribution of the Fraunhofer diffraction region corresponding to the optimized turning angle distribution is as follows. Figure 13 As shown; according to formula (16), the intensity distribution of the final metasurface at a specified distance under a specified wavelength and polarization state is obtained as follows. Figure 14 As shown, encrypted images can only be observed after the decryption conditions are met; otherwise, the encrypted information cannot be displayed.

[0112] Example 2:

[0113] Example 2 provides a multi-channel information encryption display device based on metasurfaces, which is fabricated using the design method for a multi-channel information encryption display device based on metasurfaces as described in Example 1. The structure of the multi-channel information encryption display device based on metasurfaces provided in Example 2 is shown below. Figure 3 , Figure 4 .

[0114] Since the device provided in Example 2 corresponds to the design method provided in Example 1, the structure and function of the device can be understood by referring to Example 1, and will not be repeated here.

[0115] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A design method for a multi-channel information encryption display device based on metasurfaces, characterized in that, Includes the following steps: Step 1: Construct the basic structure of a multi-channel information encryption display device based on a metasurface. The basic structure includes a substrate and a nanobrick array on the substrate. The substrate is divided into multiple unit structures of the same size. The nanobrick array includes several nanobricks with the same size parameters. Each unit structure and one nanobrick on its working surface constitute a nanobrick structure unit. The size parameters of the nanobrick structure unit are optimized so that the function of the nanobrick structure unit is equivalent to a micro / nano half-wave plate when the design wavelength is perpendicularly incident. Step 2: Use a polarizer to generate linearly polarized light with intensity I0, polarization direction α1 and designed wavelength. The linearly polarized light is incident perpendicularly on the nanobrick structure unit and then passes through an analyzer with polarization direction α2. The first functional relationship between the first outgoing light intensity I1 and the polarization direction α1 of the linearly polarized light, the turning angle θ of the nanobrick in the nanobrick structure unit, and the polarization direction α2 of the analyzer is obtained. Design a first image, which is a grayscale image without encrypted information. Based on the grayscale distribution of the first image and the first function relationship, calculate four alternative values ​​for the turning angle θ of the nanobrick in each nanobrick structural unit. Step 3: Keeping the transmission axis directions of the polarizer and the analyzer unchanged, rotate the nanobrick structure unit by a first angle to obtain a second functional relationship between the second emitted light intensity I2 and the polarization direction α1 of the linearly polarized light, the turning angle θ of the nanobrick in the nanobrick structure unit, and the polarization direction α2 of the analyzer; design a second image, which is an image containing the encrypted image design wavelength and design polarization state information; Based on the intensity distribution of the second image and the second functional relationship, two candidate values ​​are selected from the four candidate values ​​of the turning angle θ of the nanobrick. Step 4: Design the third and fourth images. The third image is an image containing the encryption image design distance information, and the fourth image is an encryption image. Using the simulated annealing algorithm, determine the final value from multiple alternative values ​​of the turning angle θ of the nanobricks in each nanobrick structural unit. Arrange the nanobrick array according to the determined turning angle θ of the nanobricks to obtain a multi-channel information encryption display device based on metasurface. Linearly polarized light with intensity I0, polarization direction α1, and a designed wavelength is incident on the multi-channel information encryption display device based on a metasurface, and the first image is displayed after passing through an analyzer with polarization direction α2; keeping the transmission axis directions of the polarizer and the analyzer unchanged, the multi-channel information encryption display device based on a metasurface is rotated by the first angle to display the second image, and the designed wavelength and designed polarization state information of the encrypted image are obtained; When coherent light waves with designed wavelengths and designed polarization states are incident on the multi-channel information encryption display device based on metasurfaces, the third image can be observed in the Fraunhofer diffraction region, and the encrypted image design distance information can be obtained. The fourth image can be observed at a designed distance by incident coherent light with a designed wavelength and a designed polarization state.

2. The design method of the multi-channel information encryption display device based on metasurface according to claim 1, characterized in that, The dimensional parameters include the major axis L, minor axis W, and height H of the nanobrick, as well as the side length C of the working surface of the unit structure; the major axis L and minor axis W are not equal; an xoy coordinate system is established with the directions parallel to the two sides of the working surface as the x-axis and y-axis, respectively, and the turning angle θ of the nanobrick is the angle between the major axis L of the nanobrick and the x-axis.

3. The design method for a multi-channel information encryption display device based on metasurfaces according to claim 1, characterized in that, The first functional relationship is expressed as: I′1=cos 2 (2θ-α2-α1); where I′1 represents the normalized intensity of the first emitted light intensity I1; the second functional relationship is expressed as: In the formula, I′2 represents the normalized intensity of the second emitted light intensity I2. Indicates the first angle.

4. The design method of the multi-channel information encryption display device based on metasurface according to claim 3, characterized in that, When the transmission axis of the polarizer is perpendicular to the transmission axis of the analyzer, α2 = α1 + π / 2, and the first angle When π / 8 is taken, the first functional relationship is expressed as: I′1=cos 2 (2θ-2α²-π / 2); the second functional relationship is expressed as: I′²=cos 2 (2θ-2α2-3π / 4).

5. The design method of a multi-channel information encryption display device based on metasurfaces according to claim 4, characterized in that, Take α1=-π / 4, α2=π / 4, then I′1=cos 2 (2θ), I′2=cos 2 (2θ-π / 4).

6. The design method of the multi-channel information encryption display device based on metasurface according to claim 1, characterized in that, The second image is a binary image.

7. The design method of a multi-channel information encryption display device based on metasurfaces according to claim 1, characterized in that, The four alternative values ​​for the turning angle θ of the nanobrick satisfy the following: θ0 is the first alternative angle.

8. The design method of a multi-channel information encryption display device based on metasurfaces according to claim 1, characterized in that, The evaluation function used when employing the simulated annealing algorithm is: In the formula, cost is the evaluation function, M1 and N1 are the number of rows and columns of pixels in the first image, respectively; I3 is the light intensity distribution in the Fraunhofer diffraction region when incident at the designed wavelength; Img3 is the intensity distribution of the third image; I4 is the light intensity distribution at the designed distance in the Fresnel diffraction region when incident at the designed wavelength; and Img4 is the intensity distribution of the fourth image.

9. The design method of a multi-channel information encryption display device based on metasurfaces according to claim 1, characterized in that, The first image has M1*N1 pixels, and the second image has M2*N2 pixels, satisfying M2<M1 and N2<N1; Based on the intensity distribution of the second image and the second functional relationship, for each nanobrick structural unit within the display area of ​​the second image, two alternative values ​​are selected from four alternative values ​​of the nanobrick's turning angle θ; for each nanobrick structural unit outside the display area of ​​the second image, the four alternative values ​​of the nanobrick's turning angle θ are retained; the display area of ​​the second image is the area used to display an image containing information on the encrypted image design wavelength and design polarization state.

10. A multi-channel information encryption display device based on metasurface, characterized in that, The device was prepared using the design method of a multi-channel information encryption display device based on metasurface as described in any one of claims 1-9.

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