Optical metasurface device and design method and manufacturing method thereof

Abstract

A design method for an optical metasurface device, the optical metasurface device comprising a substrate and a plurality of periodically arranged metastructure units on the substrate, the method comprising: acquiring a unit pattern representing a corresponding metastructure unit, the unit pattern comprising a pixel array having a plurality of pixels, each pixel having a first state or a second state; in response to determining that the transmission performance of the metastructure unit does not meet a preset condition, cyclically performing the following operations: determining the weights of the plurality of pixels; based on the weights, randomly flipping the state of one or more pixels in a group of pixels to obtain a current unit pattern; and based on an optical simulation of the metastructure unit represented by the current unit pattern, selectively maintaining the state of the plurality of pixels or restoring the state of one or more pixels in a group of pixels to the state before the flip; in response to determining that the transmission performance of the metastructure unit meets a preset condition, generating descriptive information defining the optical metasurface device.

Description

Technical Field

[0001] This disclosure relates to the field of optical technology, and in particular to an optical metasurface device and its design and manufacturing methods. Background Technology

[0002] Optical metasurfaces are a new type of artificially designed material that achieves extraordinary properties, possessing optical characteristics not found in natural materials. Metasurfaces can shape the wavefront, polarization, transmission properties, and nonlinear response of light in various ways, demonstrating unique capabilities in light manipulation and providing a novel platform for the design of miniaturized, high-performance micro / nano optical devices.

[0003] Optical devices that enable specific manipulation of light (e.g., one-way transmission, one-way reflection) have wide applications in various technological fields. However, in related technologies, such optical devices are complex to design and their large size makes integration difficult. Summary of the Invention

[0004] It would be beneficial to provide a mechanism to alleviate, reduce, or even eliminate one or more of the aforementioned problems.

[0005] According to one aspect of this disclosure, a design method for an optical metasurface device is provided. The optical metasurface device includes a substrate and a plurality of periodically arranged metastructure units on the substrate. The method includes: acquiring a unit pattern representing a corresponding metastructure unit among the plurality of metastructure units, wherein the unit pattern includes a pixel array having a plurality of pixels, each of the plurality of pixels having a first state or a second state, the first state indicating that metamaterial exists at the position corresponding to the pixel in the metastructure unit, and the second state indicating that metamaterial does not exist at the position corresponding to the pixel in the metastructure unit; determining, based on optical simulation of the metastructure unit, that the transmission performance of the metastructure unit does not meet a preset condition; in response to determining that the transmission performance of the metastructure unit does not meet the preset condition, performing the following operations cyclically: determining the weights of each of the plurality of pixels; randomly flipping the state of one or more pixels among the plurality of pixels based on the weights to obtain a current unit pattern; and selectively maintaining the state of each of the plurality of pixels or restoring the state of one or more pixels to the state before the flip based on optical simulation of the metastructure unit represented by the current unit pattern; and generating descriptive information defining the optical metasurface device in response to determining that the transmission performance of the metastructure unit meets the preset condition.

[0006] According to another aspect of this disclosure, a method for manufacturing an optical metasurface device is provided, comprising: forming a plurality of metastructural units on a substrate using descriptive information generated in the method described above.

[0007] According to another aspect of this disclosure, an optical metasurface device is provided, which is manufactured using the method described above.

[0008] These and other aspects of this disclosure will be apparent from the embodiments described below, and will be elucidated with reference to the embodiments described below. Attached Figure Description

[0009] Further details, features, and advantages of this disclosure are disclosed in the following description of exemplary embodiments in conjunction with the accompanying drawings, in which:

[0010] Figure 1 This is a flowchart of a design method for an optical metasurface device according to exemplary embodiments of the present disclosure;

[0011] Figure 2 This is a schematic view of a cell pattern representing a metastructural unit according to an exemplary embodiment of the present disclosure;

[0012] Figure 3 This is a schematic view of an optical metasurface device according to exemplary embodiments of the present disclosure.

[0013] Figure 4 This is a flowchart of a design method for an optical metasurface device according to another exemplary embodiment of the present disclosure;

[0014] Figure 5 This is a schematic view representing the Laplacian value corresponding to a pixel according to an exemplary embodiment of the present disclosure;

[0015] Figure 6 This is a schematic view representing the Laplacian value corresponding to a pixel after multiple iterations of optimization according to an exemplary embodiment of this disclosure;

[0016] Figure 7 This is a schematic view of the transmission performance of a metastructure unit after multiple iterations of optimization according to exemplary embodiments of the present disclosure;

[0017] Figure 8 This is a schematic view of a metastructure unit under linearly polarized incident light and its transmission performance according to exemplary embodiments of the present disclosure;

[0018] Figure 9A This is a schematic view of a symmetry-extended superstructure unit according to an exemplary embodiment of the present disclosure;

[0019] Figure 9B This is a schematic view of an optical metasurface device obtained by fabricating a metasurface structure unit with symmetry extension according to an exemplary embodiment of the present disclosure;

[0020] Figure 9CThis is a schematic view of the transmission performance of an optical metasurface device according to exemplary embodiments of the present disclosure. Detailed Implementation

[0021] It will be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, areas, layers, and / or parts, these elements, components, areas, layers, and / or parts should not be limited by these terms. These terms are used only to distinguish one element, component, area, layer, or part from another. Therefore, the first element, component, area, layer, or part discussed below may be referred to as the second element, component, area, layer, or part without departing from the teachings of this disclosure.

[0022] Spatial relative terms such as “below,” “under,” “lower,” “below,” “above,” “above,” etc., may be used herein for ease of description to describe the relationship between one element or feature illustrated in the figures and another element(s). It will be understood that these spatial relative terms are intended to cover different orientations of the device in use or operation other than those depicted in the figures. For example, if the device in the figure is flipped, then an element described as “below,” “below,” or “below other elements or features” will be oriented “above other elements or features.” Thus, the exemplary terms “below” and “below” can cover both orientations above and below. Terms such as “before” or “in front” and “after” or “follow” can similarly be used, for example, to indicate the order in which light passes through the elements. Devices may be oriented in other ways (rotated 90 degrees or in other orientations) and the spatial relative descriptors used herein shall be interpreted accordingly. Additionally, it will be understood that when a layer is referred to as "between two layers," it can be the only layer between the two layers, or there can be one or more intermediate layers.

[0023] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprising” and / or “including” as used in this specification designate the presence of the stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items, and the phrase “at least one of A and B” means only A, only B, or both A and B.

[0024] It will be understood that when a component or layer is referred to as "on another component or layer," "connected to another component or layer," "coupled to another component or layer," or "adjacent to another component or layer," it may be directly on another component or layer, directly connected to another component or layer, directly coupled to another component or layer, or directly adjacent to another component or layer, or there may be intermediate components or layers. Conversely, when a component is referred to as "directly on another component or layer," "directly connected to another component or layer," "directly coupled to another component or layer," or "directly adjacent to another component or layer," no intermediate components or layers exist. However, in any case, "on" or "directly on" should not be interpreted as requiring a layer to completely cover the layer below.

[0025] Embodiments of this disclosure are described herein with reference to illustrative illustrations (and intermediate structures) of idealized embodiments. Therefore, variations in the illustrated shapes should be expected, for example, as a result of manufacturing techniques and / or tolerances. Consequently, embodiments of this disclosure should not be construed as limited to the specific shapes of the regions illustrated herein, but should include, for example, shape deviations due to manufacturing processes. Thus, the regions illustrated are schematic in nature, and their shapes are not intended to illustrate the actual shape of regions of a device and are not intended to limit the scope of this disclosure.

[0026] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having meanings consistent with their meanings in the relevant field and / or the context of this specification, and will not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0027] As used herein, the term "substrate" may refer to the substrate of a diced wafer or to the substrate of an undicated wafer. Similarly, the terms chip and die may be used interchangeably unless such interchange would cause conflict. It should be understood that the term "layer" includes thin films and, unless otherwise stated, should not be construed as indicating vertical or horizontal thickness.

[0028] Its unique spatial light conduction properties of unidirectional transmissivity and unidirectional reflection, combined with its ability to integrate ultra-thin portable devices, enable it to be used in applications such as under-display fingerprint recognition, screen panels, and cameras.

[0029] In related technologies, metamaterials that are unidirectionally transmissive and unidirectionally reflective are mostly composite systems of metals and dielectric materials, and often require 3D fabrication processes. Technologies related to unidirectional transmission are largely limited to reflectors implemented using multi-layer Bragg structures, which are relatively thick and difficult to integrate. Furthermore, unidirectional transmission systems based on silicon (Si) dielectric materials mostly operate in the infrared band.

[0030] In related technologies, unidirectional transmission devices with high isolation rely on magneto-optical effects and polarizers for filtering, transmitting only linearly polarized light. Furthermore, while magneto-optical isolators can achieve extremely high isolation rates, the thickness of the magneto-optical crystal combined with the polarizer is on the order of millimeters, limiting their use to system optical paths and making integration into portable devices difficult.

[0031] In related technologies, metal-dielectric composite systems introduce metals, causing localized hotspots to form near the metal during reverse transmission, thus achieving strong absorption. However, due to the use of the precious metal Au, electron beam lithography (EBL) or grayscale lithography is required, making mass production difficult and costly. Furthermore, the introduction of metal materials increases light transmission loss, hindering device performance optimization. Simultaneously, light also irradiates the metal during forward incidence, causing absorption and resulting in high loss and low isolation (80%-20%). If a unidirectional transmission device needs to be designed in an all-dielectric material system, the absorption loss in the metal system cannot be utilized, making it difficult to suppress reverse transmittance and posing significant challenges in material system and structural geometry selection.

[0032] Figure 1 This is a flowchart of a design method 100 for an optical metasurface device according to exemplary embodiments of the present disclosure. The optical metasurface device includes a substrate and a plurality of metastructural units periodically arranged on the substrate. Figure 1 As shown, design method 100 includes steps 110-140.

[0033] In step 110, a cell pattern representing a corresponding metastructure unit among a plurality of metastructure units is obtained. The cell pattern includes a pixel array with multiple pixels. Each pixel among the multiple pixels has a first state or a second state. The first state indicates that metamaterial exists at the position corresponding to the pixel in the metastructure unit, and the second state indicates that metamaterial does not exist at the position corresponding to the pixel in the metastructure unit. In some exemplary embodiments, the refractive index of the metamaterial is greater than the refractive index of the substrate.

[0034] In step 120, based on the optical simulation of the metastructure unit, it is determined that the transmission performance of the metastructure unit does not meet the preset conditions.

[0035] Next, in response to the determination that the transmission performance of the metastructure unit does not meet the preset conditions, steps 130-1 to 130-3 are executed cyclically. In step 130-1, the weights of each of the plurality of pixels are determined. In step 130-2, based on the weights, the state of one or more pixels in a group of pixels is randomly flipped to obtain the current unit pattern. In step 130-3, based on the optical simulation of the metastructure unit represented by the current unit pattern, the states of the plurality of pixels are selectively maintained or the states of one or more pixels in a group are restored to their states before the flipping.

[0036] In step 140, in response to determining that the transmission performance of the metastructure unit meets the preset conditions, descriptive information defining the optical metasurface device is generated.

[0037] In some exemplary embodiments, multiple metastructure units are formed on a substrate using the description information generated in design method 100 to fabricate optical metasurface devices. In one example, the description information may be a process design kit (PDK) or part of a process design kit.

[0038] In summary, design method 100 employs an optimization algorithm to optimize the design of the pixel array representing the metamaterial. Based on the description information of the optical metasurface device generated by design method 100, the optical metasurface device can be manufactured. In some embodiments, the resulting optical metasurface device can meet the performance requirements of unidirectional transmission. Furthermore, in some embodiments, the substrate and metastructure units of the optical metasurface device do not include metallic materials, thereby achieving unidirectional transmission using pure dielectric materials.

[0039] In some exemplary embodiments, determining the weights of each of the multiple pixels (step 130-1) includes: calculating the Laplacian matrix corresponding to the pixel array; and assigning weights to each of the multiple pixels according to the Laplacian values ​​corresponding to the multiple pixels in the Laplacian matrix, wherein the weights of each of the multiple pixels are positively correlated with the Laplacian values ​​corresponding to the multiple pixels.

[0040] In some exemplary embodiments, randomly flipping the state of one or more pixels in a plurality of pixels (step 130-2) includes: selecting one or more pixels from the plurality of pixels according to a weight, wherein the probability of each pixel being selected in the plurality of pixels is positively correlated with the weight of that pixel; and flipping the state of one or more pixels in a plurality of pixels.

[0041] In some exemplary embodiments, selectively maintaining the respective states of multiple pixels or restoring the states of a group of one or more pixels to their states before flipping (step 130-3) includes: maintaining the respective states of multiple pixels in response to determining that the transmission performance of the metastructure unit represented by the current cell pattern is higher than the transmission performance of the metastructure unit before flipping; and restoring the states of a group of one or more pixels to their states before flipping in response to determining that the transmission performance of the metastructure unit represented by the current cell pattern is not higher than the transmission performance of the metastructure unit before flipping.

[0042] Figure 2 This is a schematic view of a cell pattern 200 representing a metastructural unit according to an exemplary embodiment of the present disclosure. Figure 2 As shown, the unit pattern 200 includes a pixel array with multiple pixels. Each pixel has a first state (in...). Figure 2 (in dark) or second state (in) Figure 2 (Represented in light color). For example, pixel 210 has a first state indicating that metamaterial is processed at the position corresponding to pixel 210 in the metastructure unit. Pixel 220 has a second state indicating that no metamaterial is present at the position corresponding to pixel 220 in the metastructure unit. For example, the position corresponding to pixel 220 in the metastructure unit is air. In some exemplary embodiments, the unit pattern 200 can be generated by complete randomization.

[0043] In some exemplary embodiments, the unit pattern 200 includes 10×10 to 40×40 pixels.

[0044] In some exemplary embodiments, the optical metasurface device is fabricated by forming a plurality of metastructural units on a substrate using description information generated in the design method 100. Figure 3 This is a schematic view of an optical metasurface device 300 according to an exemplary embodiment of the present disclosure. The optical metasurface device 300 is manufactured by forming a plurality of metastructural units 310 on a substrate 320.

[0045] In some exemplary embodiments, the size of each of the plurality of metastructural units 310 ranges from 700nm×700nm to 2000nm×2000nm.

[0046] In some exemplary embodiments, the unit pattern of a corresponding superstructure unit in a plurality of superstructure units includes 10×10 to 40×40 pixels, and the size of each pixel ranges from 20nm×20nm to 60nm×60nm.

[0047] In some exemplary embodiments, the substrate 320 is made of glass, and the metamaterial 350 is made of silicon nitride (SiN).

[0048] In some exemplary embodiments, the thickness of the metamaterial 350 can be less than 1 μm, facilitating integration. For example, the thickness ranges from 100 nm to 500 nm.

[0049] In some exemplary embodiments, the minimum linewidth of the metastructure unit 310 can be flexibly set and optimized according to the processing conditions. The optical metasurface device 300 manufactured based on this design has low requirements for process sensitivity, can effectively control the yield rate, and can achieve large-area processing.

[0050] In some exemplary embodiments, the transmission performance in method 100 is determined based on the transmission spectra of the metastructure unit under normal and reverse incidence. Normal incidence means that the metastructure unit is incident from the side of the metastructure unit away from the substrate, for example... Figure 3 The incident direction is 330. Reverse incident means that the light is incident on the substrate from the side of the substrate away from the metastructure unit, for example, incident direction 340.

[0051] In some exemplary embodiments, the preset conditions in method 100 include a transmittance greater than a first threshold and a transmittance less than a second threshold for reverse incidence. In some examples, the first threshold is greater than the second threshold.

[0052] Based on the description information of designing metastructure units 310 using method 100, an optical metasurface device 300 is fabricated by forming multiple metastructure units on a substrate 320. By designing the metastructure units 310, the optical metasurface device 300 can achieve a preset condition for incident transmittance under forward incidence 330 and a preset condition for reverse incidence transmittance under reverse incidence 340. In some embodiments, the optical metasurface device 300 can achieve unidirectional transmission and unidirectional opacity optical performance in an all-dielectric system.

[0053] Furthermore, unlike other gradient descent algorithms, the design method described in this disclosure supports optimized structural designs with different shape features and improves the upper limit of performance optimization. This is because in related technologies, pixel optimization algorithms with high degrees of freedom are generally based on heuristic learning, whose main drawback is low optimization efficiency. Theoretically, traversing all cases can yield the optimal solution, but it requires a considerable number of iterations, which is unacceptable in reality.

[0054] Figure 4 This is a flowchart of a design method 400 for an optical metasurface device according to another exemplary embodiment of this disclosure. Design method 400 is an example of design method 100. Figure 4As shown, method 400 includes steps 410 to 480.

[0055] In step 410, the element patterns of the corresponding superstructure elements in the multiple superstructure elements are randomly generated, such as element pattern 200.

[0056] In step 420, the Laplacian matrix of the pixel array included in the unit pattern is calculated.

[0057] In step 430, weights are assigned to the pixels based on their respective Laplacian values ​​in the Laplacian matrix, and the states of one or more pixels are randomly flipped. In some exemplary embodiments, the weights of the pixels are positively correlated with their corresponding Laplacian values. For example, a pixel with a Laplacian value of 0 can be assigned a weight of 0; a pixel with a Laplacian value of 1 can be assigned a weight of 1; a pixel with a Laplacian value of 2 can be assigned a weight of 2; a pixel with a Laplacian value of 3 can be assigned a weight of 4; and a pixel with a Laplacian value of 4 can be assigned a weight of 8. After assigning weights to each pixel, they are randomly selected according to their weights, with pixels having a higher probability of being selected. The selected pixels are flipped from their existing states. For example, a pixel in a first state is flipped to a second state. Correspondingly, at the position corresponding to this pixel in the metastructure unit, the state with processed metamaterial is flipped to a state without metamaterial, such as air.

[0058] In some exemplary embodiments, the metastructure units can be symmetrically extended in step 440, such that multiple metastructure units are arranged symmetrically on the substrate. For example, the metastructure units can be C4 symmetrically extended. The C4 symmetrically extended metastructure units coincide with themselves when rotated by any 90°. The metasurface fabricated via the symmetrically extended metastructure units is insensitive to the polarization state of the incident light. In some embodiments, the metasurface possesses unidirectional transmission and unidirectional reflection optical properties regardless of whether the incident light is linearly polarized or unpolarized.

[0059] In step 450, based on the optical simulation of the metastructure unit, it is determined whether the transmission performance of the flipped metastructure unit is improved. In some exemplary embodiments, the optical simulation may employ the finite-difference time-domain method (FDTD). FDTD calculates the forward and reverse transmission spectra of the metastructure unit represented by the current unit pattern under forward and reverse incident conditions, and calculates its reward function (transmission performance / unidirectional transmission performance). If the transmission performance of the metastructure unit is improved, the current unit pattern is retained. Otherwise, in step 460, the state of the flipped pixel is restored to its state before the flip.

[0060] In step 470, it is determined whether the transmission performance of the metastructure unit meets the preset conditions. If the preset conditions are met, the iterative optimization process ends, and in step 480, description information defining the optical metastructure surface device is generated. In one example, the description information may be a process design kit (PDK). If the preset conditions are not met, the process returns to step 430, and the state of one or more pixels is randomly flipped again according to the weights.

[0061] Based on the description information of the optical metastructure surface device generated by design method 400, an optical metastructure surface device that meets predetermined performance requirements can be manufactured. Design method 400 performs biased random selection by assigning weights according to the Laplacian matrix, also known as Laplacian binary search. Compared with the direct binary search method without weight assignment, i.e., selecting with exactly the same probability, design method 400 improves the efficiency of optimization.

[0062] Figure 5 This is a schematic view representing the Laplacian value corresponding to a pixel according to an exemplary embodiment of this disclosure. Figure 5 As shown, the upper part 510 represents the pixel array corresponding to the superstructure unit, and the lower part 520 represents the Laplacian matrix calculated for each pixel array. For example, the Laplacian value corresponding to pixel 512 is 4 (indicated by reference numeral 522 in the figure).

[0063] Figure 6 This is a schematic view representing the Laplacian value corresponding to a pixel after multiple iterations of optimization, according to exemplary embodiments of this disclosure. In some exemplary embodiments, the iterative optimization method may be as described in method 100, method 400, or other embodiments. Figure 6 As shown, 610 represents the cell pattern corresponding to the superstructure unit generated in each iteration of the multiple iterations of optimization (i-vi). 620 represents the Laplacian matrix calculated based on each cell pattern in the multiple iterations of optimization. 630 represents the distribution relationship between the Laplacian value and the corresponding number of pixels. In 630, the horizontal axis represents the Laplacian value, and the vertical axis represents the number of pixels. It can be seen that in the first few iterations of optimization, most pixels have large Laplacian values. At this time, the pixels selected for flipping are almost completely random. Since the Laplacian values ​​of pixels located at the edges and protruding positions of the superstructure unit are larger, pixels at the edges and protruding positions can be selected for flipping. Therefore, as the number of iterations of optimization increases, a large number of pixels have small Laplacian values. At the same time, most pixels are located inside the superstructure unit, with only a small number located at the edges of the superstructure unit.

[0064] Figure 7 This is a schematic view of the transmission performance of a metastructure unit after multiple iterations of optimization, according to exemplary embodiments of the present disclosure. Figure 7 As shown, the horizontal axis represents the number of iterations, and the vertical axis represents the transmission performance of the metastructure unit. Curve 710 indicates the relationship between the number of iterations and transmission performance when using the Laplace binary search according to embodiments of this disclosure. Curve 720 indicates the relationship between the number of iterations and transmission performance when using a direct binary search. Figure 7 As can be seen, the Laplace binary search method described in this disclosure significantly improves optimization efficiency compared to the direct binary search method. In some embodiments, it can also avoid the occurrence of linewidths that are difficult to process.

[0065] In summary, the Laplacian binary search described in this disclosure can dynamically allocate the weight of each selected pixel for flipping based on the pixel's proximity relationship. This approach can accommodate the diversity in the early stages of optimization iterations and converge to an acceptable optimal value relatively quickly. Furthermore, in this algorithm, independent pixels have larger Laplacian values ​​and higher selection weights, thus eliminating the existence of such independent pixels and avoiding linewidths that are difficult to process.

[0066] Figure 8 This is a schematic view of a metastructure unit and its transmission performance under linearly polarized incident light according to exemplary embodiments of the present disclosure. Under linearly polarized incident light, a metastructure unit with unidirectional transmission and unidirectional reflection functions can also be obtained based on the methods of embodiments of the present disclosure. Figure 8 As shown, 810 represents the polarization direction of the incident light. 820 represents the unit pattern corresponding to the metastructure unit obtained through iterative optimization under this incident light. 830 represents the transmission performance corresponding to the metastructure unit represented by 820, where the horizontal axis represents the wavelength (nm) of the incident light and the vertical axis represents the transmittance. The curve indicated by 832 represents the forward transmittance, and the curve indicated by 834 represents the reverse transmittance.

[0067] Figure 9A This is a schematic view of a symmetrically extended metastructure unit cell according to exemplary embodiments of the present disclosure. In some exemplary embodiments, a plurality of metastructure units are arranged in a symmetrically extended manner on a substrate to obtain a metasurface insensitive to polarized light. Figure 9A The five superstructure units shown are each extended with C4 symmetry. For example, the superstructure unit indicated by 910 is extended via, as shown in... Figure 6 The superstructure unit generated by 610 during vi iteration is obtained by C4 symmetry extension.

[0068] Figure 9B This is a schematic view of an optical metasurface device obtained by fabricating a metasurface structure unit with symmetry extension according to an exemplary embodiment of the present disclosure. Figure 9B As shown, select Figure 9A The superstructure unit 910, which is extended with C4 symmetry, is used for fabrication. For example, electron beam direct writing can be used to fabricate it, and the scanning electron microscope sample characterization is shown in 920. By selecting from a large number of potential structures, structures that meet the minimum linewidth requirements under different processes can be obtained.

[0069] Figure 9C This is a schematic view of the transmission performance of an optical metasurface device according to exemplary embodiments of the present disclosure. Figure 9C As shown, the horizontal axis represents the wavelength (nm) of the incident light, and the vertical axis represents the transmittance of the optical metasurface device 920 obtained through experimental processing. Figure 9C In the diagram, curve 930 represents the transmittance for normal incidence, and curve 940 represents the transmittance for reverse incidence. Normal incidence refers to light incident from the direction of the metamaterial (e.g., ...). Figure 3 (330° in the direction of the substrate); reverse incidence refers to incidence from the substrate direction (e.g., direction 330); Figure 3 (Direction 340 in the image). It can be seen that the forward transmittance of the optical metasurface device 920 is greater than 90%. When the bandwidth of the incident light is around 50 nm, the reverse transmittance of the optical metasurface device 920 is around 10%. Meanwhile, when the bandwidth of the incident light is between 400 nm and 560 nm, the reverse transmittance of the optical metasurface device 920 is less than 40%. It should be understood that, as used herein, the term unidirectional transmission refers to transmittance in one direction exceeding a predetermined threshold (e.g., 90%, 85%, 80%, etc.), without requiring transmittance in the opposite direction to be 0.

[0070] Although this disclosure has been described and illustrated in detail in the accompanying drawings and the foregoing description, such description and illustration should be considered illustrative and suggestive, not restrictive; this disclosure is not limited to the disclosed embodiments. By studying the drawings, the disclosure, and the appended claims, those skilled in the art will be able to understand and implement variations of the disclosed embodiments in practice with respect to the claimed subject matter. In the claims, the word "comprising" does not exclude other elements or steps not listed, the indefinite article "a" or "an" does not exclude a plurality, and the term "a plurality" means two or more. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be beneficial.

Claims

1. A design method for an optical metasurface device, the optical metasurface device comprising a substrate and a plurality of periodically arranged metastructural units on the substrate, the method comprising: Obtain a unit pattern representing a corresponding superstructure unit among the plurality of superstructure units, wherein the unit pattern includes a pixel array having a plurality of pixels, each of the plurality of pixels having a first state or a second state, the first state indicating that there is metamaterial at the position corresponding to the pixel in the superstructure unit, and the second state indicating that there is no metamaterial at the position corresponding to the pixel in the superstructure unit; Based on optical simulation of the metastructure unit, it was determined that the transmission performance of the metastructure unit did not meet the preset conditions. In response to the determination that the transmission performance of the metastructure unit does not meet the preset conditions, the following first to third steps are executed cyclically: In the first step, the weights of each of the plurality of pixels are determined, including: Calculate the Laplacian matrix corresponding to the pixel array; and Based on the Laplacian values ​​corresponding to the plurality of pixels in the Laplacian matrix, weights are assigned to the plurality of pixels respectively, wherein the weights of the plurality of pixels are positively correlated with the Laplacian values ​​corresponding to the plurality of pixels respectively; In the second step, based on the weights, the state of one or more pixels in a group of pixels is randomly flipped to obtain the current unit pattern; and In the third step, based on the optical simulation of the metastructure unit represented by the current unit pattern, the states of the plurality of pixels are selectively maintained or the states of one or more pixels are restored to their states before the flip; and In response to determining that the transmission performance of the metastructure unit satisfies the preset condition, descriptive information defining the optical metasurface device is generated.

2. The method of claim 1, wherein, The state of randomly flipping one or more pixels among the plurality of pixels includes: Based on the weights, select one or more pixels from the plurality of pixels, wherein the probability of each pixel being selected is positively correlated with the pixel's weight; and Flip the state of the group of one or more pixels.

3. The method of claim 1, wherein, The selective maintenance of the individual states of the plurality of pixels or the restoration of the state of the group of one or more pixels to the state before the flip includes: In response to determining that the transmittance of the metastructure unit represented by the current cell pattern is higher than the transmittance of the metastructure unit before flipping, the respective states of the plurality of pixels are maintained; and In response to determining that the transmission performance of the metastructure unit represented by the current unit pattern is not higher than the transmission performance of the metastructure unit before flipping, the state of the group of one or more pixels is restored to the state before flipping.

4. The method according to any one of claims 1-3, wherein, The transmission performance is determined based on the transmission spectra of the metastructure unit under normal and reverse incidence, where normal incidence means that the metastructure unit is incident on the side of the metastructure unit away from the substrate, and reverse incidence means that the substrate is incident on the side of the substrate away from the metastructure unit.

5. The method of claim 4, wherein, The preset conditions include that the transmittance of the forward incident light is greater than a first threshold, and the transmittance of the reverse incident light is less than a second threshold, wherein the first threshold is greater than the second threshold.

6. The method according to any one of claims 1-3, wherein, The plurality of metastructure units are arranged in a symmetrically extended manner on the substrate.

7. The method according to any one of claims 1-3, wherein, The refractive index of the metamaterial is greater than that of the substrate.

8. A method for manufacturing an optical metasurface device, comprising: The plurality of metastructure units are formed on the substrate using the description information generated in any one of claims 1 to 7.

9. An optical metasurface device, said optical metasurface device being manufactured using the method of claim 8.

10. The device of claim 9, wherein, The size range of each of the plurality of superstructural units is... to .

11. The device of claim 9, wherein, The element patterns of the corresponding superstructure units in the plurality of superstructure units include to 1 pixel; and wherein the size range of each pixel is 1. to .

12. The device of claim 9, wherein, The thickness range of the metamaterial is: to .

13. The device according to any one of claims 9-12, wherein, The substrate is made of glass, and the metamaterial is made of silicon nitride.

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