Design Method and Device, Equipment, Medium of Circular Dichroism Polarization Device

Abstract

The present disclosure relates to a design method, device, equipment, and medium of a circular dichroism polarization device. The method includes obtaining a first design pattern of a target design layer of the circular dichroism polarization device, where the first design pattern is used to indicate the initial refractive index distribution of the target design layer in a first iterative calculation process, and the first iterative calculation process represents any iterative calculation process; performing electromagnetic field simulation based on the first design pattern to obtain the gradient of the objective function with respect to the refractive index distribution, where the objective function is the difference between the left-handed circular polarization transmittance and the right-handed circular polarization transmittance; updating the first design pattern along the gradient direction with the maximization of the objective function as the goal, and repeating the above steps for iterative calculation until a target design pattern is obtained, where the target design pattern is a binary image. According to the embodiments of the present disclosure, a design pattern with an arbitrary shape can be obtained, improving the design freedom and design efficiency.

Description

Technical Field

[0001] The present disclosure relates to the field of micro-nano optical device design, and particularly to a design method, device, equipment, and medium for a circular dichroism polarization device. Background Art

[0002] Polarization, as one of the basic properties of light waves, can provide physical information that cannot be provided by other optical parameters. Using the polarization of light for imaging detection, rich information can be obtained based on the analysis of the polarization parameters of light. In particular, circularly polarized light has special research and application value due to its propagation characteristics different from other polarization states. For example, in a turbid medium, circularly polarized light has a memory effect, and its polarization retention ability during transmission is stronger than that of linearly polarized light. Using circular polarization information can further improve the quality of image restoration; in addition, in biomedical imaging, circularly polarized light also has special information transfer ability because it is independent of the anisotropic components in the sample. The technology for obtaining circular polarization information thus has important application value in fields such as marine science, remote sensing detection, biomedical detection, machine vision, photography and videography, and autonomous driving.

[0003] The current mainstream circular polarization detection method relies on the combination of a quarter-wave plate and a linear polarizer. First, the circular polarization state is converted into a linearly polarized state in a specific direction through a quarter-wave plate, and then filtered and detected through an analyzer. Since this method utilizes the birefringence effect of crystals, there are certain requirements for the thickness and size of the device in principle, and it is difficult to achieve high integration. In recent years, optical metasurfaces have used the arrangement of sub-micron-sized micro-nano structures to achieve the regulation of various optical parameters through the interaction mechanism between light and matter at the sub-wavelength scale. In terms of polarization modulation and detection, in 2017, Jingpei Hu et al. proposed applying a dielectric metasurface to circular polarization detection and designed a metasurface design scheme with a Z-shaped structure; in 2018, the Capasso research group achieved approximately 90% circular dichroism in the visible light band using planar micro-nano structures; in 2019, this research group proposed a compact full Stokes parameter measurement system based on a metasurface.

[0004] However, the existing metasurface structure designs mainly adopt the forward design method, based on simple geometric shapes. For specific wavelength, material, and structure size requirements, a certain-scale database needs to be constructed under the target design conditions through methods such as parameter scanning. The design process is relatively time-consuming, and the design freedom is severely limited, failing to fully utilize the polarization modulation ability of the metasurface; furthermore, the control of wide spectral bands, large incident angle ranges, processing technology errors, etc. will significantly increase the design complexity, making the design efficiency of the metasurface the main factor restricting its application and promotion. Summary of the Invention

[0005] In view of this, the present disclosure provides a design method, device, equipment, and medium for a circular dichroism polarization device, which can obtain a design pattern with an arbitrary shape, improving the design freedom and design efficiency.

[0006] According to one aspect of the present disclosure, there is provided a topology optimization design method for a circular dichroism polarization device, including:

[0007] Obtain a first design pattern of a target design layer of the circular dichroism polarization device, where the first design pattern is used to indicate the initial refractive index distribution of the target design layer in a first iterative calculation process, and the first iterative calculation process represents any iterative calculation process;

[0008] Perform electromagnetic field simulation based on the first design pattern to obtain the gradient of the objective function with respect to the refractive index distribution, where the objective function is the difference between the left-handed circular polarization transmittance and the right-handed circular polarization transmittance;

[0009] Along the gradient direction, with the maximization of the objective function as the goal, update the first design pattern, and repeat the above steps for iterative calculation until a target design pattern is obtained, where the target design pattern is a binary image.

[0010] In a possible implementation manner, the performing electromagnetic field simulation based on the first design pattern to obtain the gradient of the objective function with respect to the refractive index distribution includes:

[0011] Perform smoothing filtering and binarization processing on the first design pattern to obtain a second design pattern;

[0012] Perform electromagnetic field simulation based on the second design pattern to obtain a first forward electric field distribution, a first adjoint electric field distribution, a second forward electric field distribution, and a second adjoint electric field distribution, where the first forward electric field distribution and the first adjoint electric field distribution respectively represent the forward electric field distribution and the adjoint electric field distribution in the target design layer when left-handed circularly polarized light is incident, and the second forward electric field distribution and the second adjoint electric field distribution respectively represent the forward electric field distribution and the adjoint electric field distribution in the target design layer when right-handed circularly polarized light is incident;

[0013] Determine the gradient of the objective function with respect to the refractive index distribution according to the first forward electric field distribution, the first adjoint electric field distribution, the second forward electric field distribution, and the second adjoint electric field distribution.

[0014] In a possible implementation manner, the performing smoothing filtering and binarization processing on the first design pattern to obtain a second design pattern includes:

[0015] Perform smoothing filtering on the first design pattern to obtain a third design pattern, where the value of each pixel point of the third design pattern is continuously distributed;

[0016] Binarize the third design pattern based on a first parameter to obtain the second design pattern. The first parameter represents the binarization parameter used in the first iteration stage. The first parameter includes a first binarization threshold and a first binarization coefficient. The first binarization threshold is used to distinguish the processing method of the value of each pixel point in the third design pattern, and the first binarization coefficient is used to indicate the adjustment amplitude of the value of each pixel point in the third design pattern. The first binarization coefficient increases as the number of iterations increases.

[0017] In a possible implementation, the electromagnetic field simulation based on the second design pattern to obtain a first forward electric field distribution, a first adjoint electric field distribution, a second forward electric field distribution, and a second adjoint electric field distribution includes:

[0018] Obtain a first design parameter, where the first design parameter represents the design parameter used in the first iterative calculation. The first design parameter at least includes a preset wavelength and a preset angle;

[0019] Simulate the first forward electric field distribution in the target design layer when the left-handed circularly polarized light is incident on the circular dichroism polarization device at the preset angle, where the working wavelength of the target design layer is the preset wavelength; and simulate the second forward electric field distribution in the target design layer when the right-handed circularly polarized light is incident on the circular dichroism polarization device at the preset angle;

[0020] Use the first TE component and the first TM component as excitation sources to simulate the first adjoint electric field distribution in the target design layer when the first TE component and the first TM component are incident on the circular dichroism polarization device in the reverse direction. The first TE component and the first TM component respectively represent the outgoing TE component and the outgoing TM component corresponding to the left-handed circularly polarized light; and use the second TE component and the second TM component as excitation sources to simulate the second adjoint electric field distribution in the target design layer when the second TE component and the second TM component are incident on the circular dichroism polarization device in the reverse direction. The second TE component and the second TM component respectively represent the outgoing TE component and the outgoing TM component corresponding to the right-handed circularly polarized light.

[0021] In a possible implementation, the method further includes:

[0022] When simulating the incidence of the left-handed circularly polarized light, determine the first transmittance of the first TE component and the second transmittance of the first TM component; and when simulating the incidence of the right-handed circularly polarized light, determine the third transmittance of the second TE component and the fourth transmittance of the second TM component;

[0023] Determining the gradient of the objective function with respect to the refractive index distribution according to the first forward electric field distribution, the first adjoint electric field distribution, the second forward electric field distribution, and the second adjoint electric field distribution includes:

[0024] Determining the gradient of the left-handed circular polarization transmittance with respect to the refractive index distribution according to the first transmittance, the second transmittance, the first forward electric field distribution, and the first adjoint electric field distribution; and determining the gradient of the right-handed circular polarization transmittance with respect to the refractive index distribution according to the third transmittance, the fourth transmittance, the second forward electric field distribution, and the second adjoint electric field distribution;

[0025] Determining the gradient of the objective function with respect to the refractive index distribution according to the gradient of the left-handed circular polarization transmittance with respect to the refractive index distribution and the gradient of the right-handed circular polarization transmittance with respect to the refractive index distribution.

[0026] In a possible implementation manner, the method further includes:

[0027] Initializing design parameters, where the design parameters include at least one of a working wavelength, an incident angle, a degradation pattern, and a material thickness.

[0028] In a possible implementation manner, updating the first design pattern along the gradient direction with the maximization of the objective function as the goal includes:

[0029] When the design parameters include a degradation pattern, performing a weighted calculation on the first gradient and the second gradient, and updating the first design pattern along the weighted gradient direction with the maximization of the objective function as the goal;

[0030] Wherein, the first gradient represents the gradient of the objective function with respect to the refractive index distribution obtained by performing electromagnetic field simulation based on the first design pattern; the second gradient represents the gradient of the objective function with respect to the refractive index distribution obtained by performing electromagnetic field simulation based on the degradation pattern.

[0031] In a possible implementation manner, the degradation pattern includes a dilation pattern and / or an erosion pattern, the first parameter further includes a second binarization threshold and a third binarization threshold, the second binarization threshold is less than the first binarization threshold, the third binarization threshold is greater than the first binarization threshold, and the method further includes:

[0032] Performing binarization processing on the first design pattern based on the second binarization threshold and the first binarization coefficient to obtain the dilation pattern;

[0033] and / or,

[0034] Binarize the first design pattern based on the third binarization threshold and the first binarization coefficient to obtain the etching pattern.

[0035] In a possible implementation, the circular dichroism polarization device includes multiple design layers, and the multiple design layers include the target design layer. The method further includes:

[0036] Obtain the gradient corresponding to each design layer in the multiple design layers, where the gradient corresponding to the target design layer is the gradient of the objective function with respect to the refractive index distribution obtained by performing electromagnetic field simulation based on the first design pattern;

[0037] Updating the first design pattern along the gradient direction with the maximization of the objective function as the goal includes:

[0038] Update the first design pattern along the direction of the mean of the gradients corresponding to each design layer with the maximization of the objective function as the goal.

[0039] In a possible implementation, when the first iterative calculation process is the first iterative calculation process, the first design pattern is a randomly generated design pattern;

[0040] When the first iterative calculation process is not the first iterative calculation process, the first design pattern is the design pattern output by the previous iterative calculation process of the first iterative calculation process.

[0041] According to another aspect of the present disclosure, there is provided a topological optimization design device for a circular dichroism polarization device, including:

[0042] A pattern acquisition module configured to acquire a first design pattern of the target design layer of the circular dichroism polarization device, where the first design pattern is used to indicate the initial refractive index distribution of the target design layer in the first iterative calculation process, and the first iterative calculation process represents any iterative calculation process;

[0043] A simulation module configured to perform electromagnetic field simulation based on the first design pattern to obtain the gradient of the objective function with respect to the refractive index distribution, where the objective function is the difference between the left-handed circular polarization transmittance and the right-handed circular polarization transmittance;

[0044] An update module configured to update the first design pattern along the gradient direction with the maximization of the objective function as the goal, and repeat the above steps for iterative calculation until a target design pattern is obtained, where the target design pattern is a binary image.

[0045] In a possible implementation, the simulation module is further configured to:

[0046] Perform smoothing filtering and binarization on the first design pattern to obtain a second design pattern;

[0047] Perform electromagnetic field simulation based on the second design pattern to obtain a first forward electric field distribution, a first adjoint electric field distribution, a second forward electric field distribution, and a second adjoint electric field distribution, where the first forward electric field distribution and the first adjoint electric field distribution respectively represent the forward electric field distribution and the adjoint electric field distribution in the target design layer when left-handed circularly polarized light is incident, and the second forward electric field distribution and the second adjoint electric field distribution respectively represent the forward electric field distribution and the adjoint electric field distribution in the target design layer when right-handed circularly polarized light is incident;

[0048] Determine the gradient of the objective function with respect to the refractive index distribution according to the first forward electric field distribution, the first adjoint electric field distribution, the second forward electric field distribution, and the second adjoint electric field distribution.

[0049] In a possible implementation manner, the performing smoothing filtering and binarization on the first design pattern to obtain a second design pattern includes:

[0050] Perform smoothing filtering on the first design pattern to obtain a third design pattern, and the value of each pixel point of the third design pattern is continuously distributed;

[0051] Perform binarization on the third design pattern based on a first parameter to obtain the second design pattern, where the first parameter represents the binarization parameter used in the first iteration process, the first parameter includes a first binarization threshold and a first binarization coefficient, the first binarization threshold is used to distinguish the processing method of the value of each pixel point in the third design pattern, the first binarization coefficient is used to indicate the adjustment amplitude of the value of each pixel point in the third design pattern, and the first binarization coefficient increases as the number of iterations increases.

[0052] In a possible implementation manner, the performing electromagnetic field simulation based on the second design pattern to obtain a first forward electric field distribution, a first adjoint electric field distribution, a second forward electric field distribution, and a second adjoint electric field distribution includes:

[0053] Obtain a first design parameter, where the first design parameter represents the design parameter used in the first iterative calculation, and the first design parameter at least includes a preset wavelength and a preset angle;

[0054] Simulate the first forward electric field distribution in the target design layer when the left-handed circularly polarized light is incident on the circular dichroic polarization device at the preset angle, where the working wavelength of the target design layer is the preset wavelength; and simulate the second forward electric field distribution in the target design layer when the right-handed circularly polarized light is incident on the circular dichroic polarization device at the preset angle;

[0055] Take the first transverse electric wave (TE) component and the first transverse magnetic wave (TM) component as excitation sources, and simulate the first adjoint electric field distribution in the target design layer when the first TE component and the first TM component are incident on the circular dichroic polarization device in the reverse direction. The first TE component and the first TM component respectively represent the outgoing TE component and the outgoing TM component corresponding to the left-handed circularly polarized light; and take the second TE component and the second TM component as excitation sources, and simulate the second adjoint electric field distribution in the target design layer when the second TE component and the second TM component are incident on the circular dichroic polarization device in the reverse direction. The second TE component and the second TM component respectively represent the outgoing TE component and the outgoing TM component corresponding to the right-handed circularly polarized light.

[0056] In a possible implementation manner, the device further includes:

[0057] A determination module, where the determination module is configured to determine a first transmittance of the first TE component and a second transmittance of the first TM component when simulating the incidence of the left-handed circularly polarized light; and determine a third transmittance of the second TE component and a fourth transmittance of the second TM component when simulating the incidence of the right-handed circularly polarized light;

[0058] The determining the gradient of the objective function with respect to the refractive index distribution according to the first forward electric field distribution, the first adjoint electric field distribution, the second forward electric field distribution, and the second adjoint electric field distribution includes:

[0059] Determine the gradient of the left-handed circularly polarized transmittance with respect to the refractive index distribution according to the first transmittance, the second transmittance, the first forward electric field distribution, and the first adjoint electric field distribution; and determine the gradient of the right-handed circularly polarized transmittance with respect to the refractive index distribution according to the third transmittance, the fourth transmittance, the second forward electric field distribution, and the second adjoint electric field distribution;

[0060] Determine the gradient of the objective function with respect to the refractive index distribution according to the gradient of the left-handed circularly polarized transmittance with respect to the refractive index distribution and the gradient of the right-handed circularly polarized transmittance with respect to the refractive index distribution.

[0061] In a possible implementation manner, the device further includes:

[0062] Initialization module, the initialization module is configured to initialize design parameters, the design parameters including at least one of a working wavelength, an incident angle, a degradation pattern, and a material thickness.

[0063] In a possible implementation manner, the update module is further configured to:

[0064] In the case where the design parameter includes a degradation pattern, perform a weighted calculation on a first gradient and a second gradient, and along the weighted gradient direction, with the maximization of the objective function as the goal, update the first design pattern;

[0065] Wherein, the first gradient represents the gradient of the objective function with respect to the refractive index distribution obtained by performing electromagnetic field simulation based on the first design pattern; the second gradient represents the gradient of the objective function with respect to the refractive index distribution obtained by performing electromagnetic field simulation based on the degradation pattern.

[0066] In a possible implementation manner, the degradation pattern includes a dilation pattern and / or an erosion pattern, the first parameter further includes a second binarization threshold and a third binarization threshold, the second binarization threshold is less than the first binarization threshold, the third binarization threshold is greater than the first binarization threshold, and the device further includes:

[0067] Dilation module, the dilation module is configured to perform binarization processing on the first design pattern based on the second binarization threshold and the first binarization coefficient to obtain the dilation pattern;

[0068] and / or,

[0069] Erosion module, the erosion module is configured to perform binarization processing on the first design pattern based on the third binarization threshold and the first binarization coefficient to obtain the erosion pattern.

[0070] In a possible implementation manner, the circular dichroism polarization device includes a plurality of design layers, the plurality of design layers includes the target design layer, and the device further includes:

[0071] Gradient acquisition module, the gradient acquisition module is further configured to acquire the gradient corresponding to each design layer in the plurality of design layers, wherein the gradient corresponding to the target design layer is the gradient of the objective function with respect to the refractive index distribution obtained by performing electromagnetic field simulation based on the first design pattern;

[0072] The update module is further configured to:

[0073] Along the direction of the mean value of the gradients corresponding to each design layer, with the maximization of the objective function as the goal, update the first design pattern.

[0074] In a possible implementation, when the first iterative calculation process is the first iterative calculation process, the first design pattern is a randomly generated design pattern;

[0075] When the first iterative calculation process is not the first iterative calculation process, the first design pattern is the design pattern output by the previous iterative calculation process of the first iterative calculation process.

[0076] According to another aspect of the present disclosure, there is provided an electronic device, including: a processor; a memory for storing processor-executable instructions; wherein, the processor is configured to implement the above method when executing the instructions stored in the memory.

[0077] According to another aspect of the present disclosure, there is provided a non-volatile computer-readable storage medium, on which computer program instructions are stored, wherein, the computer program instructions implement the above method when executed by a processor.

[0078] In the embodiments of the present disclosure, the gradient of the refractive index distribution at each location of the target design layer when designing the target design layer according to the first design pattern is obtained through electromagnetic field simulation, and then the first design pattern is updated based on the gradient, so that a design pattern with an arbitrary shape can be obtained, improving the design freedom and design efficiency.

[0079] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and do not limit the present disclosure. Other features and aspects of the present disclosure will become clear according to the following detailed description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] The accompanying drawings included in the specification and constituting a part of the specification illustrate exemplary embodiments, features and aspects of the present disclosure, and are used to explain the principles of the present disclosure.

[0081] Figure 1 A flowchart showing a topology optimization design method for a circular dichroism polarization device provided according to an embodiment of the present disclosure.

[0082] Figure 2 A schematic diagram showing a short-wave infrared circular dichroism polarization filter provided according to an embodiment of the present disclosure.

[0083] Figure 3 A schematic diagram showing one pattern period provided according to an embodiment of the present disclosure.

[0084] Figure 4 A schematic diagram showing a short-wave infrared circular dichroism polarization filter provided according to an embodiment of the present disclosure.

[0085] Figure 5A flowchart showing a topological optimization design method for a circular dichroism polarization device provided according to an embodiment of the present disclosure.

[0086] Figure 6 A schematic diagram showing design results obtained based on different random initial patterns provided according to an embodiment of the present disclosure.

[0087] Figure 7 A schematic diagram showing the evolution of the pattern with the number of iterations during the optimization process provided according to an embodiment of the present disclosure.

[0088] Figure 8 Show the Figure 7 A schematic diagram showing the change in the transmittance of left- and right-handed circularly polarized light corresponding thereto.

[0089] Figure 9 Show the Figure 7 A schematic diagram showing the change in the binarization parameter corresponding thereto.

[0090] Figure 10 A schematic diagram showing the evolution of the pattern with the number of iterations during the optimization process provided according to an embodiment of the present disclosure.

[0091] Figure 11 Show the Figure 10 A schematic diagram showing the change in the transmittance of left- and right-handed circularly polarized light corresponding thereto.

[0092] Figure 12 Show the Figure 10 A schematic diagram showing the change in the binarization parameter corresponding thereto.

[0093] Figure 13 A schematic diagram showing the evolution of the pattern with the number of iterations during the optimization process provided according to an embodiment of the present disclosure.

[0094] Figure 14 Show the Figure 13 A schematic diagram showing the change in the transmittance of left- and right-handed circularly polarized light corresponding thereto.

[0095] Figure 15 Show the Figure 13 A schematic diagram showing the change in the binarization parameter corresponding thereto.

[0096] Figure 16 A schematic diagram showing the pattern obtained from the final optimization design provided according to an embodiment of the present disclosure.

[0097] Figure 17 A schematic diagram showing the transmittance curves of left- and right-handed circularly polarized light under the pattern obtained from the final optimization design provided according to an embodiment of the present disclosure.

[0098] Figure 18Schematic diagram showing the corresponding circular dichroism curve under the pattern obtained from the final optimized design provided by embodiments of the present disclosure.

[0099] Figure 19 Block diagram showing a topological optimization design device for a circular dichroism polarization device provided by embodiments of the present disclosure.

[0100] Figure 20 Block diagram showing a device for performing a topological optimization design method of a circular dichroism polarization device provided by embodiments of the present disclosure. Detailed implementation manners

[0101] Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. The same reference numerals in the drawings denote elements having the same or similar functions. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0102] The special term "exemplary" herein means "serving as an example, embodiment or illustration". Any embodiment described as "exemplary" herein is not necessarily to be construed as superior to or better than other embodiments.

[0103] In addition, for a better description of the present disclosure, numerous specific details are given in the following detailed implementation manners. Those skilled in the art should understand that the present disclosure can also be implemented without some of these specific details. In some instances, methods, means, elements and circuits well known to those skilled in the art are not described in detail so as to highlight the gist of the present disclosure.

[0104] To facilitate the understanding of those skilled in the art of the technical solutions provided by embodiments of the present disclosure, the technical environment for implementing the technical solutions will be described first below.

[0105] Polarization can provide physical information that cannot be provided by other optical parameters. Using the polarization of light for imaging detection, rich information can be obtained based on the analysis of the polarization parameters of light. In particular, circularly polarized light has special research and application values due to its propagation characteristics different from other polarization states. Therefore, the technology for obtaining circular polarization information also has important application values in the fields of marine science, remote sensing detection, biomedical detection, machine vision, photography and videography, autonomous driving, etc.

[0106] Current mainstream circular polarization detection methods rely on the combination of a quarter-wave plate and a linear polarizer. First, the circular polarization state is converted into a linear polarization state in a specific direction through the quarter-wave plate, and then filtered and detected through an analyzer. However, since this method utilizes the birefringence effect of the crystal, there are certain requirements for the thickness and size of the device in principle, making it difficult to achieve high integration. In recent years, some people have proposed applying metasurfaces to circular polarization detection and designed a metasurface design scheme with a Z-shaped structure. However, the existing metasurface structure designs mainly adopt the forward design method, based on simple geometric shapes. For specific wavelength, material, and structural size requirements, a certain scale of database needs to be constructed under the target design conditions through methods such as parameter scanning. The design process is relatively time-consuming, and the design freedom is severely limited, failing to fully utilize the polarization modulation ability of metasurfaces. In addition, the control of wide spectral bands, large incident angle ranges, processing technology errors, etc. will significantly increase the design complexity, making the design efficiency of metasurfaces the main factor restricting their application and promotion. Therefore, it is of great significance to study the design of circular dichroism polarization devices.

[0107] The topological optimization design method of the circular dichroism polarization device provided by the embodiments of the present disclosure obtains the gradient of the refractive index distribution at each place of the target design layer when designing the target design layer according to the first design pattern through electromagnetic field simulation, and then updates the first design pattern based on the gradient, so as to obtain a design pattern with an arbitrary shape, improving the design freedom and design efficiency.

[0108] Figure 1 The flowchart showing the topological optimization design method of the circular dichroism polarization device provided by the embodiments of the present disclosure is as Figure 1 shown. The method may include:

[0109] S101. Obtain the first design pattern of the target design layer of the circular dichroism polarization device, where the first design pattern is used to indicate the initial refractive index distribution of the target design layer in the first iterative calculation process, and the first iterative calculation process represents any iterative calculation process.

[0110] S102. Perform electromagnetic field simulation based on the first design pattern to obtain the gradient of the objective function with respect to the refractive index distribution. The objective function (Figure of merit, FoM) is the difference between the left-handed circular polarization transmittance T L and the right-handed circular polarization transmittance T R .

[0111] S103. Along the gradient direction, with the maximization of the objective function as the goal, update the first design pattern, and repeat the above steps for iterative calculation until the target design pattern is obtained. The target design pattern is a binary image.

[0112] In step S101, the first iterative calculation process can represent any iterative calculation process.

[0113] When the first iterative calculation process is the first iterative calculation process, the first design pattern is a randomly generated design pattern, that is, the initial design pattern (such as the following ρ O (r)). The first design pattern can be obtained by appropriately smoothing a random matrix determined by initializing design parameters. Among them, the initializing design parameters can include an initialization algorithm and defined optimization parameters. The design parameters involved can include, but are not limited to, basic physical parameters (such as illumination wavelength, incident angle, material substrate, material thickness, unit period, etc.), pattern geometric constraints (such as symmetry, etc.), and gradient algorithm parameters (such as the number of iterations, update step size, step size decay rate, etc.).

[0114] In one example, the design parameters can include at least one of a working wavelength, an incident angle, a degenerate pattern, and a material thickness. Initializing the design parameters is to initialize the above design parameters.

[0115] Now, taking the design process of a short-wave infrared circular dichroism polarization filter with a working wavelength of 1500 nm as an example, the process of obtaining the first design pattern in S101 will be elaborated in detail:

[0116] Figure 2 A schematic diagram of a short-wave infrared circular dichroism polarization filter provided according to an embodiment of the present disclosure is shown. As Figure 2 shown, the expected design goal is that the metasurface filter can have a high transmittance for right circularly polarized (RCP) light, while minimizing the penetration of left circularly polarized (LCP) light as much as possible. It should be noted that after performing a mirror flip transformation on the design pattern obtained based on this goal, the metasurface structure design can achieve the opposite and equal circular dichroism (that is, achieve the transmission of left circular polarization and the reflection of right circular polarization). The metasurface filter can be designed periodically, that is, the metasurface filter is evenly divided into multiple pattern periods for design, and the design patterns of each pattern period are repeated, so that both the expected design goal can be achieved and the design efficiency can be improved. Figure 2 A shown in the figure represents a pattern period of the metasurface filter. As Figure 2 shown, the metasurface filter includes multiple such pattern periods as A.

[0117] Figure 3 A schematic diagram of a pattern period provided according to an embodiment of the present disclosure is shown. Figure 4 A schematic diagram of a short-wave infrared circular dichroism polarization filter provided according to an embodiment of the present disclosure is shown.Figure 3 The pattern period shown corresponds to Figure 2 A shown Figure 4 The polarization filter shown corresponds to Figure 3 the pattern period shown. As Figure 3 、 Figure 4 shown, for the polarization filter provided in this embodiment, at a certain operating wavelength (e.g., 1500 nm), a silicon-based dielectric metasurface can be selected as the modulation device. Specifically, a silicon modulation layer with a thickness of H (e.g., 220 nm) can be selected as the target design layer for pattern design, and quartz (silicon dioxide) can be selected as the transparent substrate. The above-mentioned silicon-based materials have mature processes and relatively low costs. Considering the case of circularly polarized light incident normally, the optimization target order is the transmission zero order. Therefore, the pattern period can be selected as P = 1000 nm, that is Figure 2 and Figure 3 the side length of A shown can be 1000 nm. After determining the basic physical parameters, for the design of the circular dichroism polarization device, C2 symmetry, that is, 180° rotational symmetry, can also be imposed on the designed pattern. In this way, the search space of the optimization design algorithm can be reduced without affecting the circular polarization dichroism of the device, and the design efficiency can be improved. In terms of the gradient algorithm parameters, the gradient algorithm usually converges to a relatively ideal design pattern after several hundred iterations. In this example, the number of iterations can be selected as 400 times, the update step size can be selected as 0.1, and the step size slowly decays at a rate of 0.99 with each iteration to ensure that the algorithm has good convergence

[0118] Generate the initial design pattern ρ O (r) based on the above-determined basic physical parameters, pattern geometric constraints, and gradient algorithm parameters. ρ O (r) can be used to indicate the initial refractive index distribution of the target design layer in the first iterative calculation process. The value of ρ O (r) is within the interval [0, 1]. A value of 0 represents that this place is etched, and a value of 1 represents that this place is not etched. In the initial stage of the algorithm, the pattern is allowed to take continuous values between [0, 1]. As the number of iterations increases, stronger binarization constraints need to be gradually imposed so that the final design result is a binarized image containing only two discrete values of 0 and 1 for processing

[0119] In the case where the first iterative calculation process is not the first iterative calculation process, the first design pattern is the design pattern output by the previous iterative calculation process of the first iterative calculation process. The generation process of the design pattern output by the previous iterative calculation process can be the same as that of the initial design pattern, which will not be elaborated here

[0120] The first iterative calculation process will be described in detail below in combination with step S102 and step S103

[0121] In step S201, electromagnetic field simulation can be performed based on the first design pattern to obtain the gradient of the objective function with respect to the refractive index distribution. Here, the objective function is the difference between the left-handed circular polarization transmittance and the right-handed circular polarization transmittance. It can be understood that when the expected design goal is that the metasurface filter can have a high transmittance for RCP light while minimizing the penetration of LCP light as much as possible, the objective function corresponds to the right-handed circular polarization transmittance minus the left-handed circular polarization transmittance; when the expected design goal is that the metasurface filter can have a high transmittance for LCP light while minimizing the penetration of RCP light as much as possible, the objective function is the left-handed circular polarization transmittance minus the right-handed circular polarization transmittance.

[0122] In a possible implementation, step S102 may include: performing smoothing filtering and binarization processing on the first design pattern to obtain a second design pattern; performing electromagnetic field simulation based on the second design pattern to obtain a first forward electric field distribution, a first adjoint electric field distribution, a second forward electric field distribution, and a second adjoint electric field distribution; determining the gradient of the objective function with respect to the refractive index distribution according to the first forward electric field distribution, the first adjoint electric field distribution, the second forward electric field distribution, and the second adjoint electric field distribution.

[0123] In a possible implementation, performing smoothing filtering and binarization processing on the first design pattern to obtain a second design pattern may include: performing smoothing filtering on the first design pattern to obtain a third design pattern; performing binarization processing on the third design pattern based on the first parameter to obtain the second design pattern.

[0124] The third design pattern is the design pattern obtained by performing smoothing filtering on the first design pattern. The value of each pixel point of the third design pattern is continuously distributed.

[0125] In an example, the first design pattern can be smoothed filtered to obtain the third design pattern through formula one.

[0126]

[0127] In the formula, both r and r′ represent three-dimensional space coordinate vectors, r represents any sampling point (i.e., pixel point) in the first design pattern, and r′ can represent the sampling point in the first design pattern that is close to r in distance; ρ O (r) represents the spatial distribution of the smoothed filtered design pattern (i.e., the first design pattern); ρ F (r) represents the spatial distribution of the design pattern after smoothing filtering (i.e., the third design pattern); w = ∑ r′ F(r, r′) is the normalized weight coefficient; F(r, r′) = max(0, R - ||r - r′||2) is the filtering function, where R is the filtering radius and R can be set as needed.

[0128] Through the above smoothing filtering operation, the refractive index value of each sampling point in the designed pattern can be updated by the weighted value of the refractive indices of the sampling points with similar distances thereto, and the weight is related to the distance between the two sampling points. After the above smoothing filtering, the third designed pattern (i.e., ρ F (r)) has a continuous numerical value distribution, that is, the value of each pixel point is continuously distributed.

[0129] After that, in order to meet the processing requirements, it is also necessary to perform binarization processing on the third designed pattern. In the embodiments of the present disclosure, the third designed pattern can be binarized based on the first parameter to obtain the second designed pattern (for example, the following ρ B (r)). Wherein, the first parameter can represent the binarization parameter used in the first iteration stage, and the first parameter can include the first binarization threshold (for example, the following η) and the first binarization coefficient (for example, the following β). In one example, the above binarization process can be implemented by Equation 2.

[0130]

[0131] In the formula, r represents a three-dimensional space coordinate vector; ρ F (r) represents the spatial distribution of the designed pattern (i.e., the third designed pattern) before binarization processing. ρ B (r) represents the spatial distribution of the designed pattern (i.e., the second designed pattern) after binarization processing. η ∈ [0, 1] is the binarization threshold, and η can be used to distinguish the processing method of the value of each pixel point in ρ F (r). When ρ F (r) is greater than or equal to 0 and less than or equal to η, the above processing method in Equation 2 is adopted. When ρ F (r) is greater than or equal to η and less than or equal to 1, the following processing method in Equation 2 is adopted. By default, η = 0.5 can be taken. β is the binarization coefficient, and β can be used to indicate the adjustment amplitude of the value of each pixel point in the third designed pattern. In the limit case of β → ∞, ρ B (r) becomes a binary pattern. Generally, the value of β can gradually increase with the increase of the number of iterations, so as to ensure that the final designed pattern is close to the binary pattern.

[0132] Through the above smoothing filtering and binarization processing steps, the lines with large curvatures in the designed pattern can be smoothed, so that a smoother pattern edge can be obtained. At the same time, the details with small sizes and unfavorable for processing in the pattern can also be removed, thereby meeting the processing requirements of high quality.

[0133] In a possible implementation, performing electromagnetic field simulation based on the second design pattern to obtain the first forward electric field distribution, the first adjoint electric field distribution, the second forward electric field distribution, and the second adjoint electric field distribution may include: obtaining first design parameters; simulating the first forward electric field distribution in the target design layer when the left-handed circularly polarized light is incident on the circular dichroic polarization device at the preset angle; using the first TE component and the first TM component as excitation sources to simulate the first adjoint electric field distribution in the target design layer when the first TE component and the first TM component are incident on the circular dichroic polarization device in the reverse direction; and using the second TE component and the second TM component as excitation sources to simulate the second adjoint electric field distribution in the target design layer when the second TE component and the second TM component are incident on the circular dichroic polarization device in the reverse direction.

[0134] During the process of electromagnetic field simulation, the first design parameters can be obtained first. Here, the first design parameters can represent the design parameters used in the first iterative calculation process, that is, the parameters involved in the electromagnetic field simulation, and can at least include a preset wavelength (such as the working wavelength of 1500 nm of the above-mentioned short-wave infrared circular dichroic polarization filter) and a preset angle (such as the following θ).

[0135] Next, forward simulation and adjoint simulation are performed on the left-handed circularly polarized light and the right-handed circularly polarized light respectively.

[0136] The process of forward simulation corresponding to the left-handed circularly polarized light is: simulating the first forward electric field distribution E L (r) in the target design layer (such as the above-mentioned silicon-based dielectric metasurface) when the left-handed circularly polarized light is incident on the circular dichroic polarization device at the preset angle θ.

[0137] Among them, r represents the three-dimensional space coordinate vector, the working wavelength of the target design layer is 1500 nm, and a second design pattern (such as the above-mentioned ρ B (r)) can be simulated on the target design layer. By simulating E L (r) in the target design layer when the left-handed circularly polarized light is incident on the circular dichroic polarization device, the transverse electric (TE) wave component of the outgoing order and the transverse magnetic (TM) wave component of the outgoing order corresponding to the left-handed circularly polarized light can be obtained, and the transmittance t LE of the transverse electric wave component of the outgoing order and the transmittance t LM of the transverse magnetic wave component of the outgoing order can be calculated. For the sake of brief description, the transverse electric wave component of the outgoing order corresponding to the left-handed circularly polarized light is now called the first TE component, the transverse magnetic wave component of the outgoing order is called the first TM component, the transmittance t LE of the transverse electric wave component of the outgoing order is called the first transmittance, and the transmittance tLM It is called the second transmittance.

[0138] Similarly, the process of forward simulation corresponding to right-handed circularly polarized light is as follows: Simulate the second forward electric field distribution E R (r) in the target design layer when the right-handed circularly polarized light is incident on the circular dichroism polarization device at a preset angle θ, and the transverse electric wave component of the outgoing order and the transverse magnetic wave component of the outgoing order corresponding to the right-handed circularly polarized light can be obtained, and the transmittance t RE of the transverse electric wave component of the outgoing order and the transmittance t RM of the transverse magnetic wave component of the outgoing order can be calculated. For the sake of concise description, the transverse electric wave component of the outgoing order corresponding to the right-handed circularly polarized light is now called the second TE component, the transverse magnetic wave component of the outgoing order is called the second TM component, the transmittance t RE of the transverse electric wave component of the outgoing order is called the third transmittance, and the transmittance t RM of the transverse magnetic wave component of the outgoing order is called the fourth transmittance.

[0139] The process of adjoint simulation corresponding to left-handed circularly polarized light is as follows: Taking the first TE component and the first TM component as new excitation sources, simulate the first adjoint electric field distributions E LAE (r) and E LAM (r) in the target design layer when the first TE component and the first TM component are incident on the circular dichroism polarization device in the reverse direction.

[0140] Similarly, the process of adjoint simulation corresponding to right-handed circularly polarized light is as follows: Taking the second TE component and the second TM component as excitation sources, simulate the second adjoint electric field distributions E RAE (r) and E RAM (r) in the target design layer when the second TE component and the second TM component are incident on the circular dichroism polarization device in the reverse direction.

[0141] The above electromagnetic field simulation can be implemented based on a variety of common electromagnetic field simulation platforms including Finite-difference time-domain (FDTD), Rigorous coupled-wave analysis (RCWA), etc. The incident left-handed circularly polarized light and right-handed circularly polarized light can be obtained by the coherent superposition of two linearly polarized lights with orthogonal polarization directions and a phase difference of 90°. In addition, the order of simulating the electric field distributions when the left-handed circularly polarized light and the right-handed circularly polarized light are incident can be carried out simultaneously or successively, and the embodiments of the present disclosure do not limit this.

[0142] In a possible implementation, determining the gradient of the objective function with respect to the refractive index distribution based on the first forward electric field distribution, the first adjoint electric field distribution, the second forward electric field distribution, and the second adjoint electric field distribution may include: determining the gradient of the left-handed circular polarization transmittance with respect to the refractive index distribution according to the first transmittance, the second transmittance, the first forward electric field distribution, and the first adjoint electric field distribution; and determining the gradient of the right-handed circular polarization transmittance with respect to the refractive index distribution according to the third transmittance, the fourth transmittance, the second forward electric field distribution, and the second adjoint electric field distribution; determining the gradient of the objective function with respect to the refractive index distribution according to the gradient of the left-handed circular polarization transmittance with respect to the refractive index distribution and the gradient of the right-handed circular polarization transmittance with respect to the refractive index distribution.

[0143] In an example, when determining the gradient of the left-handed circular polarization transmittance with respect to the refractive index distribution according to the first transmittance, the second transmittance, the first forward electric field distribution, and the first adjoint electric field distribution, Equation 3 can be used. Similarly, when determining the gradient of the right-handed circular polarization transmittance with respect to the refractive index distribution according to the third transmittance, the fourth transmittance, the second forward electric field distribution, and the second adjoint electric field distribution, Equation 4 can be used. The gradient of the left-handed circular polarization transmittance T L with respect to the dielectric constant distribution ε(r) and the right-handed circular polarization transmittance T R are as follows:

[0144]

[0145]

[0146] wherein, T L represents the left-handed circular polarization transmittance, T R represents the right-handed circular polarization transmittance, ε(r) represents the dielectric constant distribution, represents the gradient of the left-handed circular polarization transmittance T L with respect to the dielectric constant distribution ε(r), represents the gradient of the right-handed circular polarization transmittance T R with respect to the dielectric constant distribution ε(r). α is a constant related to the vacuum permittivity, the angular frequency of the light wave, etc.; E L (r), E R (r), E LAE (r), E LAM (r), E RAE (r), E RAM (r) are as described above and will not be elaborated here; respectively represent the complex conjugates of the transmittances t LE , t LM , t RE , t RM .

[0147] It should be noted that the target design layer based on the metasurface has a certain thickness. During electromagnetic field simulation, equidistant sampling can be performed along the axial direction of the metasurface, and the corresponding refractive index gradient distribution can be calculated at different positions between layers. Therefore, the average value of the refractive index gradients of each layer can be used in the subsequent gradient update of the designed pattern, which can obtain more accurate calculation results while reducing the processing difficulty.

[0148] Therefore, the circular dichroism polarization device can be regarded as including multiple design layers, and each design layer can include a target design layer. The topology optimization design method of the circular dichroism polarization device can further include: obtaining the gradient corresponding to each design layer in the multiple design layers, where the gradient corresponding to the target design layer is the gradient of the objective function with respect to the refractive index distribution obtained by electromagnetic field simulation based on the generated design pattern; thus, in the subsequent process of updating the design pattern, it can be along the direction of the mean value of the gradients corresponding to each design layer, with the maximization of the objective function as the goal, to update the design pattern.

[0149] Finally, the gradient of the objective function with respect to the refractive index distribution can be determined according to the gradient of the left-handed circular polarization transmittance with respect to the refractive index distribution and the gradient of the right-handed circular polarization transmittance with respect to the refractive index distribution, specifically referring to Equation 5.

[0150]

[0151] In the formula, T L is the left-handed circular polarization transmittance; T R is the right-handed circular polarization transmittance; ε(r) is the dielectric constant distribution; n(r) is the refractive index distribution, and FoM represents the objective function. represents the gradient of the objective function with respect to the refractive index distribution.

[0152] In the embodiments of the present disclosure, when the designed transmitted polarization state is left-handed circular polarization and the extinction polarization state is right-handed circular polarization, the corresponding objective function FoM is FoM = T L - T R ; when the designed transmitted polarization state is right-handed circular polarization and the extinction polarization state is left-handed circular polarization, the corresponding objective function FoM is FoM = T R - T L .

[0153] After calculating the gradient of the objective function with respect to the refractive index based on the field distribution of the forward simulation and the accompanying simulation, according to the optimization design goal of the circular polarization device, which is to maximize the difference in transmittance between the two circular polarization states (i.e., circular dichroism), the second design pattern after smoothing filtering and binarization can be updated along the gradient direction with the goal of maximizing the objective function, that is, the refractive index distribution of the target design layer is updated according to the gradient direction, and the above steps are repeated for iterative calculation until the algorithm converges to the final two-dimensional target design pattern, which is a binary image. Since the target design pattern is a binary image, the value of each pixel in the target design pattern is discrete, either 0 or 1. If the value of a pixel in the target design pattern is 0, it means that the area is etched, and if the value of the pixel is 1, it means that the area is not etched. Therefore, etching based on the target design pattern can obtain a circular dichroism polarization device.

[0154] The disclosed embodiments provide a micro-nano optical device design mode that is different from the traditional traversal exhaustive mode. By utilizing the reciprocity of the Green's function, the derivative of the design optimization objective function with respect to the device refractive index distribution can be explicitly calculated. By using only one forward simulation and one adjoint simulation, the derivative values at various locations in the entire sampling space can be obtained, and then the refractive index distribution at all sampling positions can be gradient updated. This can greatly improve the computational efficiency of the reverse design of micro-nano optical devices, thereby expanding the design freedom and enriching the design function goals.

[0155] In the above iterative process, a traversal sub-cycle for one or more design parameters such as working wavelength, incident angle, degradation pattern, material thickness, etc. can be selectively added according to the needs, so that a design scheme with wide band, large angle range and robust processing can be realized. For example, when a series of processes of updating the design pattern based on the preset angle θ are completed, a relatively ideal design pattern ρ1(r) can be obtained, and ρ1(r) can be used as the initial design pattern, and the above design process can be repeated under the condition of changing the degradation pattern.

[0156] In a possible implementation, the above topology optimization design method may further include: when the design parameters include the degradation pattern ρ T (r), the first gradient and the second gradient are weighted, and ρ1(r) is updated along the weighted gradient direction with the objective of maximizing the objective function. The first gradient represents the gradient of the objective function with respect to the refractive index distribution obtained by electromagnetic field simulation based on ρ1(r). The second gradient represents the gradient of the objective function with respect to the refractive index distribution obtained by electromagnetic field simulation based on ρ1(r). T (r) The gradient of the objective function obtained by electromagnetic field simulation with respect to the refractive index distribution.

[0157] In one example, the degradation pattern p T(r) may include an expansion pattern and / or an erosion pattern. Among them, the expansion pattern can be obtained by binarizing ρ1(r) based on the second binarization threshold η1 and the first binarization coefficient β, and the erosion pattern can be obtained by binarizing ρ1(r) based on the third binarization threshold η2 and the first binarization coefficient β. The second binarization threshold and the third binarization threshold can be determined based on the first binarization threshold. The second binarization threshold η1 may be less than the first binarization threshold η, and the third binarization threshold η2 may be greater than the first binarization threshold η.

[0158] It should be noted that when calculating the weighted sum of the first gradient and the second gradient, the weight coefficients can be set as needed. For example, they can both be set to 1, and the embodiments of the present disclosure do not limit this.

[0159] Figure 5 The flowchart showing the topology optimization design method of the metasurface-based circular dichroism polarization device provided by the embodiments of the present disclosure is as follows Figure 5 As shown, the topology optimization design method may include:

[0160] S501. Define the optimization parameters to obtain an initial design pattern;

[0161] S502. Perform smoothing filtering and binarization processing on the initial design pattern;

[0162] S503. Through electromagnetic field simulation, calculate the forward field distribution and the adjoint field distribution of left-handed circularly polarized light and right-handed circularly polarized light incident on the target design layer, i.e., the metasurface, respectively;

[0163] S504. Calculate the refractive index gradient according to the forward field distribution and the adjoint field distribution, use the difference between the transmissive and extinction polarization state gradients as the update direction, and update the design pattern;

[0164] S505. Repeat the above steps to traverse multiple parameters such as wavelengths, incident angles, and degradation patterns until an optimized design pattern is obtained.

[0165] S501 to S505 can be referred to above and will not be elaborated here.

[0166] In the embodiments of the present disclosure, in S505, two degradation cases of pattern dilation and erosion are considered to simulate the actual degradation process of the processed pattern. For this purpose, η can be made to fluctuate up and down near 0.5, and η1 = 0.2 and η2 = 0.8 are taken to obtain the dilated pattern and the eroded pattern respectively. For each degraded pattern, forward simulation, adjoint simulation are respectively carried out and the gradient distribution is calculated, and gradient backpropagation is carried out according to the degradation model to obtain the gradient distribution of the original designed pattern. The final updated gradient can be calculated by the weighted sum of the gradients corresponding to each degraded pattern. Among them, the weight coefficients of the non-degraded pattern ρ1(r) and the two degraded patterns, namely the dilated pattern and the eroded pattern, can be both 1, and the sum of the three is used to obtain the final updated gradient. Incorporating pattern degradation into the optimization process in this way to simulate the errors that may occur in actual processing can maximize the robustness of the designed pattern to processing errors.

[0167] In addition, different random initial patterns can be obtained by using different random matrices. When the topology optimization design of the circular polarizer is subsequently carried out using different random initial patterns, the topology optimization design algorithm may converge the designed pattern to different solutions. Figure 6 The schematic diagram shows the preliminary design results obtained by the algorithm after 400 iterations under 9 different random initial patterns. Figure 7 shows the use of Figure 6 The schematic diagram shows the evolution of the pattern with the number of iterations during the algorithm optimization process in the case of one of the initial patterns of the preliminary design results shown. Figure 8 shows the same as Figure 7 The schematic diagram shows the change of the left- and right-handed circular polarization light transmittance corresponding thereto. Figure 9 shows the same as Figure 7 The schematic diagram shows the change of the binarization parameter corresponding thereto.

[0168] Among the candidate design patterns obtained from the preliminary design, the candidate solutions can be analyzed according to the actual situations such as transmittance and pattern processing difficulty, and some of the selected solutions can be further optimized and designed. Figure 10 shows the use of Figure 6 The schematic diagram shows the evolution of the pattern with the number of iterations when the second-round design is carried out using a more refined sampling interval and higher calculation accuracy for one of the preliminary design solutions of the preliminary design results shown. Figure 11 shows the same as Figure 10 The schematic diagram shows the change of the left- and right-handed circular polarization light transmittance corresponding thereto. Figure 12 shows the same as Figure 10 The schematic diagram shows the change of the binarization parameter corresponding thereto. As Figures 10 to 12 shown, one of the preliminary design solutions of the preliminary design results shown can be used, and the process of the second-round design using a more refined sampling interval and higher calculation accuracy. Based on Figure 6 the schematic diagram shows one of the preliminary design results, the process of the second-round design using a more refined sampling interval and higher calculation accuracy.Figure 10 The shown design result can continue to be used for the third-round design with a finer sampling interval and higher calculation accuracy. Figure 13 It shows the Figure 10 schematic diagram of the evolution of the pattern with the number of iterations during the third-round design using a finer sampling interval and higher calculation accuracy based on the design result of Figure 14 It shows the Figure 13 schematic diagram of the change in the transmittance of left- and right-handed circularly polarized light corresponding to Figure 15 It shows the Figure 13 schematic diagram of the change in the corresponding binarization parameter.

[0169] Figure 16 It shows the schematic diagram of the pattern obtained from the final optimized design. Figure 17 It shows the schematic diagram of the transmittance curves of left- and right-handed circularly polarized light under the pattern obtained from the final optimized design. Figure 18 It shows the schematic diagram of the corresponding circular dichroism curve under the pattern obtained from the final optimized design. As Figure 17 , Figure 18 shown, at the design wavelength of 1500 nm, the transmittances of the metasurface for normally incident left- and right-handed circularly polarized light are 0.033 and 0.989 respectively, and the corresponding circular dichroism value is 0.956.

[0170] The topology optimization design method of the circular dichroism polarization device based on the metasurface provided by the embodiments of the present disclosure performs topology optimization design based on gradient update, and can obtain design patterns with arbitrary shapes, having a higher design freedom compared with the design method based on simple geometric shape parameter scanning; secondly, by controlling parameters such as wavelength, incident angle, and degraded pattern, the design of a circular polarization dichroism device with wide spectrum, large angle, and processing robustness can be realized.

[0171] The embodiments of the present disclosure also provide a topology optimization design device for a circular dichroism polarization device. Figure 19 It shows the flowchart of the topology optimization design method of the circular dichroism polarization device provided by the embodiments of the present disclosure. As Figure 19 shown, the topology optimization design device 190 of the circular dichroism polarization device may include a pattern acquisition module 191, a simulation module 192, and an update module 193.

[0172] Figure 19 The pattern acquisition module 191 shown can be configured to acquire the first design pattern of the target design layer of the circular dichroism polarization device, and the first design pattern is used to indicate the initial refractive index distribution of the target design layer during the first iterative calculation process, and the first iterative calculation process represents any iterative calculation process. Figure 19The simulation module 192 shown can be configured to perform electromagnetic field simulation based on the first design pattern to obtain the gradient of the objective function with respect to the refractive index distribution, where the objective function is the difference between the left-handed circular polarization transmittance and the right-handed circular polarization transmittance. Figure 19 The update module 193 shown can be configured to update the first design pattern along the gradient direction with the aim of maximizing the objective function, and repeat the above steps for iterative calculation until the target design pattern is obtained, where the target design pattern is a binary image.

[0173] In a possible implementation, the simulation module can also be configured to:

[0174] Perform smoothing filtering and binarization on the first design pattern to obtain a second design pattern;

[0175] Perform electromagnetic field simulation based on the second design pattern to obtain a first forward electric field distribution, a first adjoint electric field distribution, a second forward electric field distribution, and a second adjoint electric field distribution, where the first forward electric field distribution and the first adjoint electric field distribution respectively represent the forward electric field distribution and the adjoint electric field distribution in the target design layer when left-handed circularly polarized light is incident, and the second forward electric field distribution and the second adjoint electric field distribution respectively represent the forward electric field distribution and the adjoint electric field distribution in the target design layer when right-handed circularly polarized light is incident;

[0176] Determine the gradient of the objective function with respect to the refractive index distribution according to the first forward electric field distribution, the first adjoint electric field distribution, the second forward electric field distribution, and the second adjoint electric field distribution.

[0177] In a possible implementation, performing smoothing filtering and binarization on the first design pattern to obtain a second design pattern may include:

[0178] Perform smoothing filtering on the first design pattern to obtain a third design pattern, where the value of each pixel point of the third design pattern is continuously distributed;

[0179] Perform binarization on the third design pattern based on a first parameter to obtain a second design pattern, where the first parameter represents the binarization parameter used in the first iteration stage, the first parameter includes a first binarization threshold and a first binarization coefficient, the first binarization threshold is used to distinguish the processing method of the value of each pixel point in the third design pattern, the first binarization coefficient is used to indicate the adjustment amplitude of the value of each pixel point in the third design pattern, and the first binarization coefficient increases with the increase of the number of iterations.

[0180] In a possible implementation, performing electromagnetic field simulation based on the second design pattern to obtain a first forward electric field distribution, a first adjoint electric field distribution, a second forward electric field distribution, and a second adjoint electric field distribution may include:

[0181] Obtain a first design parameter, where the first design parameter represents the design parameter used in the first iterative calculation process, and the first design parameter includes at least a preset wavelength and a preset angle;

[0182] Simulate the first forward electric field distribution in the target design layer when left-handed circularly polarized light is incident on the circular dichroism polarization device at the preset angle, where the working wavelength of the target design layer is the preset wavelength; and, simulate the second forward electric field distribution in the target design layer when right-handed circularly polarized light is incident on the circular dichroism polarization device at the preset angle;

[0183] Use the first transverse electric wave (TE) component and the first transverse magnetic wave (TM) component as excitation sources to simulate the first adjoint electric field distribution in the target design layer when the first TE component and the first TM component are incident on the circular dichroism polarization device in the reverse direction. The first TE component and the first TM component respectively represent the outgoing TE component and the outgoing TM component corresponding to the left-handed circularly polarized light; and, use the second TE component and the second TM component as excitation sources to simulate the second adjoint electric field distribution in the target design layer when the second TE component and the second TM component are incident on the circular dichroism polarization device in the reverse direction. The second TE component and the second TM component respectively represent the outgoing TE component and the outgoing TM component corresponding to the right-handed circularly polarized light.

[0184] In a possible implementation manner, the device may further include:

[0185] A determination module, where the determination module may be configured to determine a first transmittance of the first TE component and a second transmittance of the first TM component when simulating the incidence of left-handed circularly polarized light; and, determine a third transmittance of the second TE component and a fourth transmittance of the second TM component when simulating the incidence of right-handed circularly polarized light;

[0186] Determine the gradient of the objective function with respect to the refractive index distribution according to the first forward electric field distribution, the first adjoint electric field distribution, the second forward electric field distribution, and the second adjoint electric field distribution, including:

[0187] Determine the gradient of the left-handed circular polarization transmittance with respect to the refractive index distribution according to the first transmittance, the second transmittance, the first forward electric field distribution, and the first adjoint electric field distribution; and, determine the gradient of the right-handed circular polarization transmittance with respect to the refractive index distribution according to the third transmittance, the fourth transmittance, the second forward electric field distribution, and the second adjoint electric field distribution;

[0188] Determine the gradient of the objective function with respect to the refractive index distribution according to the gradient of the left-handed circular polarization transmittance with respect to the refractive index distribution and the gradient of the right-handed circular polarization transmittance with respect to the refractive index distribution.

[0189] In a possible implementation, the above-mentioned device may further include an initialization module, which may be configured to initialize design parameters, where the design parameters include at least one of a working wavelength, an incident angle, a degradation pattern, and a material thickness.

[0190] In a possible implementation, the updating module may further be configured to:

[0191] When the design parameter includes a degradation pattern, perform a weighted calculation on the first gradient and the second gradient, and update the first design pattern along the direction of the weighted gradient with the maximization of the objective function as the goal;

[0192] Wherein, the first gradient represents the gradient of the objective function with respect to the refractive index distribution obtained by performing electromagnetic field simulation based on the first design pattern; the second gradient represents the gradient of the objective function with respect to the refractive index distribution obtained by performing electromagnetic field simulation based on the degradation pattern.

[0193] In a possible implementation, the degradation pattern includes a dilation pattern and / or an erosion pattern, the first parameter further includes a second binarization threshold and a third binarization threshold, the second binarization threshold is less than the first binarization threshold, the third binarization threshold is greater than the first binarization threshold, and the device may further include:

[0194] A dilation module, which may be configured to perform binarization processing on the first design pattern based on the second binarization threshold and the first binarization coefficient to obtain a dilation pattern;

[0195] And / or,

[0196] An erosion module, which may be configured to perform binarization processing on the first design pattern based on the third binarization threshold and the first binarization coefficient to obtain an erosion pattern.

[0197] In a possible implementation, the circular dichroism polarization device includes a plurality of design layers, the plurality of design layers include a target design layer, the device may further include a gradient acquisition module, and the gradient acquisition module may further be configured to acquire the gradient corresponding to each design layer in the plurality of design layers, wherein the gradient corresponding to the target design layer is the gradient of the objective function with respect to the refractive index distribution obtained by performing electromagnetic field simulation based on the first design pattern;

[0198] The updating module may further be configured to:

[0199] Update the first design pattern along the direction of the mean value of the gradients corresponding to each design layer with the maximization of the objective function as the goal.

[0200] In a possible implementation, when the first iterative calculation process is the first iterative calculation process, the first design pattern is a randomly generated design pattern;

[0201] In the case where the first iterative calculation process is not the first iterative calculation process, the first design pattern is the design pattern output by the previous iterative calculation process of the first iterative calculation process.

[0202] The topological optimization design device of the circular dichroism polarization device provided by the embodiments of the present disclosure can obtain the derivative values at various places in the entire sampling space through the simulation module, and perform gradient update on the refractive index distribution at all sampling positions through the update module, so as to obtain a design pattern with any shape, which has a higher design freedom and a higher calculation efficiency compared with the design method based on simple geometric shape parameter scanning.

[0203] In some embodiments, the functions or modules included in the topological optimization design device of the circular dichroism polarization device provided by the embodiments of the present disclosure can be used to execute the methods described in the embodiments of the topological optimization design method of the circular dichroism polarization device above. The specific implementation can refer to the description of the above method embodiments. For the sake of brevity, it will not be repeated here.

[0204] The embodiments of the present disclosure also propose a computer-readable storage medium, on which computer program instructions are stored. When the computer program instructions are executed by a processor, the above-mentioned topological optimization design method of the circular dichroism polarization device is implemented. The computer-readable storage medium can be a volatile or non-volatile computer-readable storage medium.

[0205] In some embodiments, the functions or modules included in the computer-readable storage medium provided by the embodiments of the present disclosure can be used to execute the methods described in the embodiments of the topological optimization design method of the circular dichroism polarization device above. The specific implementation can refer to the description of the above method embodiments. For the sake of brevity, it will not be repeated here.

[0206] The embodiments of the present disclosure also propose an electronic device, including: a processor; a memory for storing instructions executable by the processor; wherein, the processor is configured to implement the above-mentioned topological optimization design method of the circular dichroism polarization device when executing the instructions stored in the memory.

[0207] In some embodiments, the functions or modules included in the electronic device provided by the embodiments of the present disclosure can be used to execute the methods described in the embodiments of the topological optimization design method of the circular dichroism polarization device above. The specific implementation can refer to the description of the above method embodiments. For the sake of brevity, it will not be repeated here.

[0208] Embodiments of the present disclosure also provide a computer program product, including computer-readable code or a non-volatile computer-readable storage medium carrying the computer-readable code. When the computer-readable code runs in a processor of an electronic device, the processor in the electronic device executes the above-mentioned topology optimization design method for the circular dichroism polarization device. In some embodiments, the functions or modules included in the computer program product provided by the embodiments of the present disclosure can be used to execute the methods described in the embodiments of the above-mentioned topology optimization design method for the circular dichroism polarization device. Its specific implementation can refer to the description of the above method embodiments. For the sake of brevity, it will not be elaborated here.

[0209] Figure 20 FIG. 1900 is a block diagram of an apparatus 1900 for performing the above-mentioned topology optimization design method for a circular dichroism polarization device according to an exemplary embodiment. For example, the apparatus 1900 can be provided as a server or a terminal device. Referring to Figure 20 FIG. 1900, the apparatus 1900 includes a processing component 1922, which further includes one or more processors, and memory resources represented by a memory 1932 for storing instructions executable by the processing component 1922, such as application programs. The application programs stored in the memory 1932 can include one or more modules each corresponding to a set of instructions. In addition, the processing component 1922 is configured to execute instructions to perform the above method.

[0210] The apparatus 1900 may further include a power supply component 1926 configured to perform power management of the apparatus 1900, a wired or wireless network interface 1950 configured to connect the apparatus 1900 to a network, and an input / output interface 1958 (I / O interface). The apparatus 1900 can operate based on an operating system stored in the memory 1932, such as Windows Server TM , MacOS X TM , Unix TM , Linux TM , FreeBSD TM or the like.

[0211] In an exemplary embodiment, a non-volatile computer-readable storage medium is also provided, such as the memory 1932 including computer program instructions, and the above computer program instructions can be executed by the processing component 1922 of the apparatus 1900 to complete the above method.

[0212] The present disclosure may be a system, a method, and / or a computer program product. The computer program product may include a computer-readable storage medium having thereon computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0213] A computer-readable storage medium can be a tangible device that can hold and store instructions for use by an instruction execution device. A computer-readable storage medium can be, for example, but is not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disc (DVD), a memory stick, a floppy disk, a mechanically encoded device such as a punch card or raised structures in grooves having instructions stored thereon, and any suitable combination of the foregoing. The computer-readable storage medium as used herein is not construed as an instantaneous signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagated through a waveguide or other transmission medium (e.g., an optical pulse through an optical fiber cable), or an electrical signal transmitted through a wire.

[0214] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to respective computing / processing devices, or can be downloaded to an external computer or an external storage device through a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include a copper transmission cable, an optical fiber transmission, a wireless transmission, a router, a firewall, a switch, a gateway computer, and / or an edge server. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium in each computing / processing device.

[0215] The computer program instructions for performing the operations of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine - related instructions, microcode, firmware instructions, state - setting data, or source code or object code written in any combination of one or more programming languages, including object - oriented programming languages such as Smalltalk, C++, etc., and conventional procedural programming languages such as the "C" language or similar programming languages. The computer - readable program instructions may be executed entirely on the user's computer, partially on the user's computer, executed as a stand - alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or alternatively, may be connected to an external computer (e.g., through the Internet using an Internet service provider). In some embodiments, by using the state information of the computer - readable program instructions to customize an electronic circuit, such as a programmable logic circuit, a field - programmable gate array (FPGA), or a programmable logic array (PLA), the electronic circuit can execute the computer - readable program instructions to implement various aspects of the present disclosure.

[0216] Aspects of the present disclosure are described herein with reference to the flowchart and / or block diagram of methods, apparatus (systems), and computer program products according to embodiments of the present disclosure. It should be understood that each block of the flowchart and / or block diagram, and combinations of blocks in the flowchart and / or block diagram, can be implemented by computer - readable program instructions.

[0217] These computer - readable program instructions can be provided to a processor of a general - purpose computer, a special - purpose computer, or other programmable data - processing apparatus to produce a machine such that the instructions, when executed by the processor of the computer or other programmable data - processing apparatus, create a means for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram. These computer - readable program instructions can also be stored in a computer - readable storage medium, which causes a computer, a programmable data - processing apparatus, and / or other devices to operate in a particular manner. Thus, the computer - readable medium storing the instructions comprises a manufacture, which includes instructions for implementing various aspects of the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0218] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device, causing a series of operational steps to be performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process such that the instructions executed on the computer, other programmable data processing apparatus, or other device implement the functions / acts specified in one or more boxes of the flowchart and / or block diagram.

[0219] The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagram may represent a module, a segment of code, or a portion of an instruction, which contains one or more executable instructions for implementing the specified logical function. In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two consecutive blocks may in fact be executed substantially in parallel, or they may sometimes be executed in the reverse order, depending upon the functionality involved. It should also be noted that each block of the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or by combinations of special purpose hardware and computer instructions.

[0220] The embodiments of the present disclosure have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the market, or to enable other ordinary skilled persons in the art to understand the embodiments disclosed herein.

Claims

1. A topological optimization design method for a circular dichroism polarization device, characterized in that, Including: Obtaining a first design pattern of a target design layer of the circular dichroism polarization device, where the first design pattern is used to indicate an initial refractive index distribution of the target design layer in a first iterative calculation process, and the first iterative calculation process represents any one iterative calculation process; Performing electromagnetic field simulation based on the first design pattern to obtain a gradient of an objective function with respect to the refractive index distribution, where the objective function is the difference between the left-handed circular polarization transmittance and the right-handed circular polarization transmittance; Along the gradient direction, aiming at maximizing the objective function, updating the first design pattern, and repeating the above steps for iterative calculation until a target design pattern is obtained, where the target design pattern is a binary image.

2. The method according to claim 1, characterized in that, The performing electromagnetic field simulation based on the first design pattern to obtain a gradient of the objective function with respect to the refractive index distribution includes: Performing smoothing filtering and binarization processing on the first design pattern to obtain a second design pattern; Performing electromagnetic field simulation based on the second design pattern to obtain a first forward electric field distribution, a first adjoint electric field distribution, a second forward electric field distribution, and a second adjoint electric field distribution, where the first forward electric field distribution and the first adjoint electric field distribution respectively represent the forward electric field distribution and the adjoint electric field distribution in the target design layer when left-handed circularly polarized light is incident, and the second forward electric field distribution and the second adjoint electric field distribution respectively represent the forward electric field distribution and the adjoint electric field distribution in the target design layer when right-handed circularly polarized light is incident; Determining the gradient of the objective function with respect to the refractive index distribution according to the first forward electric field distribution, the first adjoint electric field distribution, the second forward electric field distribution, and the second adjoint electric field distribution.

3. The method according to claim 2, wherein The performing smoothing filtering and binarization processing on the first design pattern to obtain a second design pattern includes: Performing smoothing filtering on the first design pattern to obtain a third design pattern, where the value of each pixel point of the third design pattern is continuously distributed; Performing binarization processing on the third design pattern based on a first parameter to obtain the second design pattern, where the first parameter represents a binarization parameter used in the first iterative stage process, and the first parameter includes a first binarization threshold and a first binarization coefficient. The first binarization threshold is used to distinguish the processing method of the value of each pixel point in the third design pattern, and the first binarization coefficient is used to indicate the adjustment amplitude of the value of each pixel point in the third design pattern, and the first binarization coefficient increases with the increase of the number of iterations.

4. The method according to claim 2, wherein The performing electromagnetic field simulation based on the second design pattern to obtain a first forward electric field distribution, a first adjoint electric field distribution, a second forward electric field distribution, and a second adjoint electric field distribution includes: Obtaining a first design parameter, where the first design parameter represents a design parameter used in the first iterative calculation process, and the first design parameter at least includes a preset wavelength and a preset angle; Simulate the first forward electric field distribution in the target design layer when the left-handed circularly polarized light is incident on the circular dichroic polarization device at the preset angle, where the working wavelength of the target design layer is the preset wavelength; and simulate the second forward electric field distribution in the target design layer when the right-handed circularly polarized light is incident on the circular dichroic polarization device at the preset angle; Use the first TE component and the first TM component as excitation sources to simulate the first adjoint electric field distribution in the target design layer when the first TE component and the first TM component are incident on the circular dichroic polarization device in the reverse direction. The first TE component and the first TM component respectively represent the outgoing TE component and the outgoing TM component corresponding to the left-handed circularly polarized light; and use the second TE component and the second TM component as excitation sources to simulate the second adjoint electric field distribution in the target design layer when the second TE component and the second TM component are incident on the circular dichroic polarization device in the reverse direction. The second TE component and the second TM component respectively represent the outgoing TE component and the outgoing TM component corresponding to the right-handed circularly polarized light.

5. The method according to claim 4, wherein The method further includes: When simulating the incidence of the left-handed circularly polarized light, determine the first transmittance of the first TE component and the second transmittance of the first TM component; and when simulating the incidence of the right-handed circularly polarized light, determine the third transmittance of the second TE component and the fourth transmittance of the second TM component; The determining the gradient of the objective function with respect to the refractive index distribution according to the first forward electric field distribution, the first adjoint electric field distribution, the second forward electric field distribution, and the second adjoint electric field distribution includes: Determine the gradient of the left-handed circularly polarized transmittance with respect to the refractive index distribution according to the first transmittance, the second transmittance, the first forward electric field distribution, and the first adjoint electric field distribution; and determine the gradient of the right-handed circularly polarized transmittance with respect to the refractive index distribution according to the third transmittance, the fourth transmittance, the second forward electric field distribution, and the second adjoint electric field distribution; Determine the gradient of the objective function with respect to the refractive index distribution according to the gradient of the left-handed circularly polarized transmittance with respect to the refractive index distribution and the gradient of the right-handed circularly polarized transmittance with respect to the refractive index distribution.

6. The method according to claim 3, wherein The method further includes: Initialize the design parameters, where the design parameters include at least one of the working wavelength, the incident angle, the degradation pattern, and the material thickness.

7. The method according to claim 6, wherein Updating the first design pattern along the gradient direction with the maximization of the objective function as the goal includes: When the design parameters include the degradation pattern, perform weighted calculation on the first gradient and the second gradient, and update the first design pattern along the weighted gradient direction with the maximization of the objective function as the goal; Wherein, the first gradient represents the gradient of the objective function with respect to the refractive index distribution obtained by electromagnetic field simulation based on the first design pattern; the second gradient represents the gradient of the objective function with respect to the refractive index distribution obtained by electromagnetic field simulation based on the degradation pattern.

8. The method according to claim 7, wherein The degenerate pattern includes a dilation pattern and / or an erosion pattern. The first parameter further includes a second binarization threshold and a third binarization threshold. The second binarization threshold is less than the first binarization threshold, and the third binarization threshold is greater than the first binarization threshold. The method further includes: Performing binarization processing on the first design pattern based on the second binarization threshold and the first binarization coefficient to obtain the dilation pattern; and / or, Performing binarization processing on the first design pattern based on the third binarization threshold and the first binarization coefficient to obtain the erosion pattern.

9. The method according to claim 1, characterized in that, The circular dichroism polarization device includes a plurality of design layers, and the plurality of design layers include the target design layer. The method further includes: Obtaining the gradient corresponding to each design layer in the plurality of design layers, where the gradient corresponding to the target design layer is the gradient of the objective function with respect to the refractive index distribution obtained by performing electromagnetic field simulation based on the first design pattern; Updating the first design pattern along the gradient direction with the maximization of the objective function as the goal, including: Updating the first design pattern along the direction of the mean of the gradients corresponding to each design layer with the maximization of the objective function as the goal.

10. The method according to claim 1, wherein In the case where the first iterative calculation process is the first iterative calculation process, the first design pattern is a randomly generated design pattern; In the case where the first iterative calculation process is not the first iterative calculation process, the first design pattern is the design pattern output by the previous iterative calculation process of the first iterative calculation process.

11. A topological optimization design device for a circular dichroism polarization device, characterized in that, including: A pattern acquisition module configured to acquire a first design pattern of a target design layer of the circular dichroism polarization device, where the first design pattern is used to indicate the initial refractive index distribution of the target design layer in the first iterative calculation process, and the first iterative calculation process represents any iterative calculation process; A simulation module configured to obtain the gradient of the objective function with respect to the refractive index distribution by performing electromagnetic field simulation based on the first design pattern, where the objective function is the difference between the left-handed circular polarization transmittance and the right-handed circular polarization transmittance; An update module configured to update the first design pattern along the gradient direction with the maximization of the objective function as the goal, and repeat the above steps for iterative calculation until a target design pattern is obtained, where the target design pattern is a binary image.

12. The device according to claim 11, wherein The simulation module is further configured to: Perform smoothing filtering and binarization processing on the first design pattern to obtain a second design pattern; Perform electromagnetic field simulation based on the second design pattern to obtain a first forward electric field distribution, a first adjoint electric field distribution, a second forward electric field distribution, and a second adjoint electric field distribution, where the first forward electric field distribution and the first adjoint electric field distribution respectively represent the forward electric field distribution and the adjoint electric field distribution in the target design layer when left-handed circularly polarized light is incident, and the second forward electric field distribution and the second adjoint electric field distribution respectively represent the forward electric field distribution and the adjoint electric field distribution in the target design layer when right-handed circularly polarized light is incident; Determine the gradient of the objective function with respect to the refractive index distribution according to the first forward electric field distribution, the first adjoint electric field distribution, the second forward electric field distribution, and the second adjoint electric field distribution.

13. The device according to claim 12, characterized in that, The obtaining the second design pattern by performing smoothing filtering and binarization processing on the first design pattern includes: Perform smoothing filtering on the first design pattern to obtain a third design pattern, where the values of each pixel point of the third design pattern are continuously distributed; Perform binarization processing on the third design pattern based on a first parameter to obtain the second design pattern. The first parameter represents the binarization parameter used in the first iteration process, and the first parameter includes a first binarization threshold and a first binarization coefficient. The first binarization threshold is used to distinguish the processing method of the value of each pixel point in the third design pattern, and the first binarization coefficient is used to indicate the adjustment amplitude of the value of each pixel point in the third design pattern. The first binarization coefficient increases as the number of iterations increases.

14. The device according to claim 12, characterized in that, The performing electromagnetic field simulation based on the second design pattern to obtain a first forward electric field distribution, a first adjoint electric field distribution, a second forward electric field distribution, and a second adjoint electric field distribution includes: Obtain a first design parameter, where the first design parameter represents the design parameter used in the first iterative calculation, and the first design parameter at least includes a preset wavelength and a preset angle; Simulate the first forward electric field distribution in the target design layer when the left-handed circularly polarized light is incident on the circular dichroism polarization device at the preset angle, where the working wavelength of the target design layer is the preset wavelength; and simulate the second forward electric field distribution in the target design layer when the right-handed circularly polarized light is incident on the circular dichroism polarization device at the preset angle; Use the first TE component and the first TM component as excitation sources to simulate the first adjoint electric field distribution in the target design layer when the first TE component and the first TM component are incident on the circular dichroism polarization device in the reverse direction. The first TE component and the first TM component respectively represent the outgoing TE component and the outgoing TM component corresponding to the left-handed circularly polarized light; and use the second TE component and the second TM component as excitation sources to simulate the second adjoint electric field distribution in the target design layer when the second TE component and the second TM component are incident on the circular dichroism polarization device in the reverse direction. The second TE component and the second TM component respectively represent the outgoing TE component and the outgoing TM component corresponding to the right-handed circularly polarized light.

15. The device according to claim 14, characterized in that, The device further includes: A determination module configured to determine a first transmittance of the first TE component and a second transmittance of the first TM component when simulating the incidence of left-handed circularly polarized light; and to determine a third transmittance of the second TE component and a fourth transmittance of the second TM component when simulating the incidence of right-handed circularly polarized light; Determining the gradient of the objective function with respect to the refractive index distribution according to the first forward electric field distribution, the first adjoint electric field distribution, the second forward electric field distribution, and the second adjoint electric field distribution includes: Determining the gradient of the left-handed circular polarization transmittance with respect to the refractive index distribution according to the first transmittance, the second transmittance, the first forward electric field distribution, and the first adjoint electric field distribution; and determining the gradient of the right-handed circular polarization transmittance with respect to the refractive index distribution according to the third transmittance, the fourth transmittance, the second forward electric field distribution, and the second adjoint electric field distribution; Determining the gradient of the objective function with respect to the refractive index distribution according to the gradient of the left-handed circular polarization transmittance with respect to the refractive index distribution and the gradient of the right-handed circular polarization transmittance with respect to the refractive index distribution.

16. The device according to claim 13, characterized in that, The apparatus further includes: An initialization module configured to initialize design parameters, where the design parameters include at least one of a working wavelength, an incident angle, a degradation pattern, and a material thickness.

17. The device according to claim 16, wherein The update module is further configured to: When the design parameters include a degradation pattern, perform weighted calculation on the first gradient and the second gradient, and update the first design pattern along the weighted gradient direction with the maximization of the objective function as the goal; wherein the first gradient represents the gradient of the objective function with respect to the refractive index distribution obtained by performing electromagnetic field simulation based on the first design pattern; the second gradient represents the gradient of the objective function with respect to the refractive index distribution obtained by performing electromagnetic field simulation based on the degradation pattern.

18. The device according to claim 17, characterized in that, The degradation pattern includes a dilation pattern and / or an erosion pattern, the first parameter further includes a second binarization threshold and a third binarization threshold, the second binarization threshold is less than the first binarization threshold, the third binarization threshold is greater than the first binarization threshold, and the apparatus further includes: A dilation module configured to perform binarization processing on the first design pattern based on the second binarization threshold and the first binarization coefficient to obtain the dilation pattern; and / or An erosion module configured to perform binarization processing on the first design pattern based on the third binarization threshold and the first binarization coefficient to obtain the erosion pattern.

19. The device according to claim 11, characterized in that, The circular dichroism polarization device includes a plurality of design layers, the plurality of design layers includes the target design layer, and the apparatus further includes: A gradient acquisition module further configured to acquire the gradient corresponding to each design layer in the plurality of design layers, where the gradient corresponding to the target design layer is the gradient of the objective function with respect to the refractive index distribution obtained by performing electromagnetic field simulation based on the first design pattern; The update module is further configured to: Update the first design pattern in the direction of the mean of the gradients corresponding to each design layer, with the maximization of the objective function as the goal.

20. The apparatus according to claim 11, wherein when the first iterative calculation process is the first iterative calculation process, the first design pattern is a randomly generated design pattern; when the first iterative calculation process is not the first iterative calculation process, the first design pattern is the design pattern output by the previous iterative calculation process of the first iterative calculation process.

21. An electronic device, characterized in that, Comprising: a processor; a memory for storing processor-executable instructions; wherein the processor is configured to implement the method according to any one of claims 1 to 10 when executing the instructions stored in the memory.

22. A non-volatile computer-readable storage medium storing computer program instructions thereon, characterized in that, The computer program instructions, when executed by a processor, implement the method according to any one of claims 1 to 10.

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