Switchable holographic metasurface design method, device, equipment and medium

Abstract

The invention provides a switchable holographic metasurface design method and device, equipment and a medium, and belongs to the field of multiplexing holographic metasurface research, and the method comprises the steps: designing a metasurface unit structure with a cylinder and a circular ring cylinder coupled, scanning the radius of the cylinder and the inner radius of the circular ring cylinder in FDTD, obtaining a relation graph of a phase and the two radiuses, and calculating the position of the metasurface unit structure according to the relation graph; and comparing the relation diagrams of the two phase-radius relations before and after the phase change. Data are analyzed by MATLAB, a two-dimensional eight-level phase sampling scheme is provided, a radius-size database before and after phase change is made, the size needed by each unit structure is selected based on the database, and switching of any two holograms can be achieved. Under the condition that only the temperature of the whole metasurface is changed, active multiplexing of the metasurface and switching of the holograms are achieved, the holographic switching step is greatly simplified, phase influences of the two holograms all come from a set of unit structures, and structural waste is avoided.

Description

Technical Field

[0001] The present invention belongs to the research field of multiplexed holographic metasurfaces, and specifically relates to a design method, device, equipment and medium for a switchable holographic metasurface. Background Art

[0002] Metasurfaces, subwavelength-scale, two-dimensional artificial metamaterials, have attracted widespread attention for their highly integrated structural properties and their unique ability to flexibly manipulate light wavefronts. By engineering the shape, size, and arrangement of metasurface microstructures, the propagation characteristics of light and electromagnetic waves (such as phase, amplitude, and polarization) can be precisely controlled. By manipulating the size and shape of the metasurface's cells, various metasurfaces with diverse applications can be designed. Holographic metasurfaces, which can generate holographic images, have garnered particular attention in recent years.

[0003] Typically, once a metasurface is designed, its physical structure is difficult to alter, making the realization of an actively tunable holographic metasurface a significant challenge. To address these challenges, researchers have recently proposed designing active holographic metasurfaces using thermally controlled holography in conjunction with phase-change materials. Zhou et al. ("Reconfigurable dielectric metasurface for active wavefront modulation based on a phase-change material metamolecule design") proposed an active dielectric metasurface with a subwavelength unit cell structure. This metasurface uses the phase-change material Ge2Sb2Se4Te1 (GSST) to achieve full-range phase or amplitude modulation in the telecommunications band. The unit cell of this metasurface consists of four cylinders of varying radius and identical height. Vortex heating is used to encode the metasurface unit cell structure. Selectively controlling the phase change of a specific GSST nanorod within the cell structure enables multi-level modulation of the phase and amplitude of light. Although this method can dynamically switch holograms, the use of vortex heating is too cumbersome and loses the advantages of metasurface integration and easy wavefront modulation. If the hologram can be switched using global heating of the metasurface, its application potential will be greatly improved.

[0004] Another approach involves designing holographic metasurfaces using phase-change materials. These materials present two different images before and after the phase change, creating a "switch" effect: "on" before the phase change and "off" after. In their work (Thermally Dependent Dynamic Meta-Holography Using Avanadium Dioxide Integrated Metasurface), Liu et al. divided the metasurface unit structures involved in modulation into two groups: one consisting solely of non-phase-change materials, and the other consisting of circular cylinder resonators composed of both phase-change and non-phase-change materials. Holographic metasurfaces were designed using these two groups of unit structures. Under low-temperature conditions, the first group primarily controls phase, while the second group, due to the influence of transmittance under these conditions, has a smaller impact on phase. Under high-temperature conditions, the first group's influence on phase is minimal, and the second group performs the primary phase modulation. This design combines phase-change materials with the design principles of geometric phase holographic metasurfaces to achieve a broadband, temperature-dependent active holographic metasurface. However, this solution still has some shortcomings. They use two sets of unit structures, but actually ignore the noise impact brought by the other set of unit structures in one set of holographic imaging. That is, the unit structure is not fully utilized for imaging, there is a certain amount of structural waste, and this waste is caused by the principle.

[0005] In short, once the traditional metasurface is designed, its physical structure is fixed and dynamic switching is difficult to achieve; existing solutions (such as vortex heating) require local precise control, which is cumbersome to operate and loses the advantages of metasurface integration; resulting in low structural utilization and easy introduction of noise during the imaging stage. Summary of the Invention

[0006] In order to solve the problems of cumbersome operation and low utilization rate of traditional metasurfaces, the present invention provides a switchable holographic metasurface design method, device, equipment and medium.

[0007] In order to achieve the above object, the present invention provides a method for designing a switchable holographic metasurface, comprising: A basic metasurface unit structure model is established; the interior of the basic metasurface unit structure model is a cylinder made of phase change material GSST, and the exterior is a ring column made of non-phase change material, and the two form a concentric cylindrical structure.

[0008] The outer radius of the circular cylinder of the basic metasurface unit structure model is kept unchanged, and the combined structures of cylindrical radii and inner radii of the circular cylinder of different sizes are simulated to obtain multiple metasurface unit structures of different sizes.

[0009] The phase change material GSST of multiple metasurface unit structures of different sizes is set to amorphous and crystalline states respectively, to obtain multiple amorphous metasurface unit structures and crystalline metasurface unit structures of different sizes; the phase change and light transmittance corresponding to each amorphous metasurface unit structure and crystalline metasurface unit structure of different sizes are calculated respectively; according to different phase change amounts and light transmittances, the phase-size data graph and transmittance-size data graph of the metasurface unit structure before and after the phase change are constructed; from the phase-size data graph and transmittance-size data graph, the size combinations that simultaneously meet the preset phase expected value and the preset transmittance threshold are screened out; based on the size combinations that meet the conditions, a phase-size database is constructed.

[0010] Based on the phase-size database and the pixel phase distribution of the two target holograms to be imaged, a unit structure size parameter that simultaneously meets the phase requirements of the two target holograms is matched for each pixel point to obtain multiple metasurface unit structures that meet the matching requirements; the multiple metasurface unit structures that meet the matching requirements are arranged and combined to form a single set of switchable holographic metasurface structures.

[0011] Preferably, the combined structure of the cylindrical radii and the inner radii of the annular cylinders of different sizes is simulated by the finite time-domain method (FDTD) to obtain a plurality of metasurface unit structures of different sizes.

[0012] Preferably, after simulating the combined structure of cylindrical radii and inner radii of circular ring columns of different sizes to obtain a plurality of supersurface unit structures of different sizes, it also includes performing numerical interpolation processing on the plurality of supersurface unit structures of different sizes, and then setting the phase change material GSST of the plurality of supersurface unit structures of different sizes to amorphous and crystalline states respectively.

[0013] Preferably, the size combinations that simultaneously meet the preset phase expected value and the preset transmittance threshold are screened out from the phase-size data graph and the transmittance-size data graph by using MATLAB data processing tools and a two-dimensional 8-level phase sampling algorithm; and a phase-size database is constructed based on the size combinations that meet the conditions.

[0014] Preferably, the phase-size database is an 8×8 phase-size database, containing 62 groups of valid data, and the storage content of the phase-size database includes: the cylindrical radius of the metasurface unit structure, the inner radius of the annular cylinder, the phase before phase change, the phase after phase change, the transmittance before phase change and the transmittance after phase change.

[0015] Preferably, the pixel point phase distribution of the two target holograms to be imaged is obtained by the GS algorithm, including: calculating the phase distribution of each pixel point of the two target holograms before and after the phase change by the GS algorithm, and matching the unit structure size parameters that simultaneously meet the phase requirements of the two target holograms for each pixel point based on the phase-size database and the phase distribution.

[0016] The present invention provides a switchable holographic metasurface design device, comprising: The structural design module is used to establish a basic metasurface unit structure model; the interior of the basic metasurface unit structure model is a cylinder made of phase change material GSST, and the exterior is a circular ring made of non-phase change material, and the two form a concentric cylindrical structure.

[0017] The database establishment module is used to keep the outer radius of the circular cylinder of the basic metasurface unit structure model unchanged, simulate the combination structure of cylindrical radii and inner radii of the circular cylinder of different sizes, and obtain multiple metasurface unit structures of different sizes; set the phase change material GSST of the multiple metasurface unit structures of different sizes to amorphous and crystalline states, respectively, to obtain multiple amorphous metasurface unit structures and crystalline metasurface unit structures of different sizes; calculate the phase change and light transmittance corresponding to each amorphous metasurface unit structure and crystalline metasurface unit structure of different sizes; construct a phase-size data graph and a transmittance-size data graph before and after the phase change of the metasurface unit structure according to different phase changes and light transmittances; screen out size combinations that simultaneously meet the preset phase expected value and the preset transmittance threshold from the phase-size data graph and the transmittance-size data graph; and construct a phase-size database based on the size combinations that meet the conditions.

[0018] The database application module is used to match the unit structure size parameters that simultaneously meet the phase requirements of the two target holograms for each pixel point based on the phase-size database and the pixel point phase distribution of the two target holograms to be imaged, thereby obtaining multiple metasurface unit structures that meet the matching requirements; and arranging and combining the multiple metasurface unit structures that meet the matching requirements to form a single set of switchable holographic metasurface structures.

[0019] The present invention also provides a computer device comprising a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement any one of the steps in the switchable holographic metasurface design method.

[0020] The present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is loaded by a processor, it can execute any one of the steps in the switchable holographic metasurface design method.

[0021] The present invention provides a switchable holographic metasurface design method with the following beneficial effects: The present invention designs a concentric cylindrical structure consisting of an internal GSST phase-change material cylinder and an external non-phase-change material ring cylinder as a metasurface unit model. By simulating combined structures with different cylinder radii and ring cylinder inner radii, the phase change and light transmittance of the corresponding unit structure are calculated in the GSST amorphous and crystalline states, respectively, and phase-size and transmittance-size data graphs before and after the phase change are constructed. From these graphs, size combinations that meet the preset phase expectation value and transmittance threshold are screened out to construct a phase-size database. Based on the database and the pixel phase distribution of the two target holograms, the unit structure size parameters that meet the phase requirements of the two images are matched for each pixel point. Finally, these unit structures are arranged and combined to form a single set of switchable dual-holographic metasurface structures; the utilization rate of the metasurface structure is maximized and resource waste is avoided; the switching of the two holograms can be completed by simply changing the temperature of the entire metasurface, and the switching steps are greatly simplified, which fundamentally reduces the energy loss and noise interference in the imaging process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To more clearly illustrate the embodiments of the present invention and its design, the following briefly introduces the drawings required for this embodiment. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0023] Figure 1 Flowchart of a method for designing a switchable holographic metasurface according to an embodiment of the present invention; Figure 2 A technical roadmap for a switchable holographic metasurface design method according to an embodiment of the present invention; Figure 3 This is a functional diagram for implementing an embodiment of the present invention; Figure 4 A diagram showing the structure of a designed metasurface unit according to an embodiment of the present invention; Figure 5 This is a data change diagram of an embodiment of the present invention; Figure 5 (a) Figure 5 (b) are data diagrams showing the phase changes with the cylinder radius and the inner radius of the ring cylinder before and after the phase transition; Figure 5 (c) Figure 5 (d) are the data diagrams of the transmittance changing with the radius of the cylinder and the inner radius of the ring cylinder before and after the phase change; Figure 6 This is an imaging effect diagram using FDTD simulation in an embodiment of the present invention. Figure 6 (a) Figure 6 (b) are the original images before and after phase change, Figure 6 (c) Figure 6 (d) are the additional phase images corresponding to the two original images respectively. Figure 6 (e), Figure 6 (f) is the imaging result of holographic imaging using the designed holographic metasurface before and after phase change; Figure 7 This is a comparison diagram of holographic imaging after setting manufacturing tolerances in an embodiment of the present invention. Figure 7 (a) Figure 7 (b) Figure 7 (c) Figure 7 (d) shows the holographic imaging results with manufacturing tolerances set to ±10nm, ±15nm, ±20nm, and ±25nm, respectively. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the technical solution of the present invention and to be able to implement it, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are not intended to limit the scope of protection of the present invention.

[0025] The present invention provides a method for designing a switchable holographic metasurface, specifically Figure 1 Shown, including: S1. Establish a basic metasurface unit structure model; the interior of the basic metasurface unit structure model is a cylinder made of phase change material GSST, and the exterior is a circular ring column made of non-phase change material, and the two form a concentric cylindrical structure.

[0026] like Figure 2 As shown, the present invention revolves around phase change metasurface holographic imaging. First, a metasurface unit structure model structure is designed; then the composite metasurface cell is simulated through FDTD, and after data interpolation processing, the size combinations that meet the phase and transmittance thresholds are screened to build a database; then, metasurface array simulation and holographic imaging are performed based on the database, and finally, MATLAB combined with the GS algorithm is used to extract the additional phase of the pixels before and after the phase change of the two target holograms. The analysis and verification are carried out from the dimensions of imaging quality, manufacturing tolerance, universality, etc., forming a closed loop of theoretical design, simulation verification, and feedback optimization to realize the hologram switching function under temperature control.

[0027] In order to realize active switching of temperature-controlled holographic metasurface, the present invention designs a unit structure of the metasurface. Based on the characteristics of this unit structure, it scans on FDTD. The favorable size is selected from the scanning results, and a two-dimensional eight-level phase sampling scheme is used to construct a size-phase database before and after temperature change. This database is used to realize a case of hologram switching, which proves the correctness of the design method.

[0028] The present invention can realize the following functions: Figure 3 As shown, simply changing the temperature of the entire metasurface, causing the phase-change material on the metasurface to undergo a phase change, can achieve holographic switching. This simple holographic switching operation preserves the integration of the holographic metasurface and fully utilizes the structure, significantly reducing the impact of structural noise compared to other solutions.

[0029] The super surface unit structure designed by the present invention is as follows Figure 4 As shown, the center is a cylinder made of the phase-change material GSST, and the outer ring is made of a non-phase-change material with a refractive index of 4.2, such as Ge. The period P of the unit structure is 900 nm, and the height H of the nanopillars in the entire unit structure is fixed at 1500 nm. Using a linearly polarized plane wave at 1550 nm, the modulated complex electric field of the periodic unit structure array was numerically calculated. The reason for this unit structure design is that when scanning the unit structure size using FDTD, two variables can be scanned: the cylinder radius and the outer radius of the ring.

[0030] When GSST changes from amorphous state to crystalline state by light or electric pulse stimulation, the refractive index and loss will increase. At a wavelength of 1550 nm, the refractive index in the amorphous state is ， When it changes to the crystalline state under external stimulation, the refractive index is The advantage of choosing GSST as the phase change material is that the refractive index of GSST before and after the phase change is large. This can make the phase change of the unit structure of the same size before and after the phase change large, paving the way for the subsequent intelligent matching to select the appropriate unit structure size.

[0031] S2. Keeping the outer radius of the circular cylinder of the basic metasurface unit structure model unchanged, simulate the combination structure of cylindrical radii of different sizes and inner radii of the circular cylinder to obtain multiple metasurface unit structures of different sizes; set the phase change material GSST of the multiple metasurface unit structures of different sizes to amorphous and crystalline states respectively, to obtain multiple amorphous metasurface unit structures and crystalline metasurface unit structures of different sizes; calculate the phase change and light transmittance corresponding to each amorphous metasurface unit structure and crystalline metasurface unit structure of different sizes respectively; construct the phase-size data diagram and transmittance-size data diagram before and after the phase change of the metasurface unit structure according to different phase changes and light transmittances; from the phase-size data diagram and transmittance-size data diagram, screen out the size combinations that simultaneously meet the preset phase expected value and the preset transmittance threshold; construct a phase-size database based on the size combinations that meet the conditions.

[0032] Specifically, the outer radius of the ring cylinder is fixed, and the finite time-domain difference method (FDTD) is used to optically simulate the metasurface unit structure with different combinations of cylinder radius and inner radius size of the ring cylinder; in the FDTD simulation environment, the phase change material GSST is set to amorphous and crystalline states respectively to obtain amorphous metasurface unit structure and crystalline metasurface unit structure; the phase change and transmittance corresponding to the amorphous and crystalline metasurface unit structures of different sizes are calculated respectively; based on the different phase change and transmittance, the phase-size data graph and transmittance-size data graph of the metasurface unit structure before and after the phase change are constructed; from the phase-size data graph and transmittance-size data graph, the size combination that simultaneously meets the phase expectation value and transmittance threshold is screened out, and based on the size combinations that meet the conditions, a phase-size database is constructed. The outer radius of the ring cylinder refers to the distance from the outer wall of the ring to the center coordinate of the ring; the inner radius of the ring cylinder refers to the distance from the inner wall of the ring to the center coordinate of the ring, and the difference between the outer radius of the ring cylinder and the inner radius of the ring cylinder is the thickness of the ring.

[0033] Next, the cylindrical radius and outer radius of the ring cylinder of the designed unit structure were scanned in FDTD. The outer radius of the ring cylinder was fixed at 315nm, the ring cylinder radius scan range was 205nm to 305nm, and the cylindrical radius scan range was 50nm to 180nm. Combining the above data, the phase change and transmittance analysis of the unit structure of each size in the periodic arrangement were numerically calculated. Scanning was performed before and after the phase change, and the phase-size data and transmittance-size data before and after the phase change were obtained, as shown in the figure below. Figure 3 As shown. By comparing the two phase-size data graphs before and after the phase change, we can find that if we want to find a phase like 2π in the data before the phase change, there can be many matching cylindrical and ring-shaped column size groups, and these groups can even be arranged and distributed from small to large after the phase change. Based on this idea, we conduct an intelligent search on these two graphs and find that we can construct an 8×8 database as shown in Table 1. This database is a core point of the present invention and a key achievement. It can be very easy to design a metasurface that can switch between two holograms. For example, before the phase change, the phase required at a certain pixel point is 2.2, and after the phase change, the phase required at the same pixel point is 0.8. Then, by comparing this 8×8 database, we can select the size of the cylinder radius of 138nm and the inner radius of the ring column of 227nm in the database at this position of the metasurface. In this way, all the unit structure sizes on the entire holographic metasurface can be matched, and it is possible to switch between two holograms before and after the phase change using a set of holographic metasurface unit structures. For example Figure 6 shown.

[0034] The database construction method is a key innovation of this invention, and some explanation is needed. First, because computer matching is used to search for suitable points (i.e., suitable size groups) between two data images, the greater the difference between the two images, the more likely it is to find suitable points. Second, this database cannot guarantee that all points will be found. In this example, after considering a certain phase tolerance, an 8×8 database was created, but only 62 suitable points were found. Some points that meet the requirements can be matched by multiple size groups. In this case, we use the transmittance-size data graph obtained above to select points with relatively high transmittance before and after the phase transition. Since we are using transmission imaging, the transmittance also determines the image quality. The two-dimensional eight-level phase sampling scheme proposed in this invention is a creative improvement over the traditional eight-level phase sampling scheme. It not only meets the main function of holographic image switching, but also has a significant feature: it can achieve eight levels of phase positioning before and after the phase transition, maximizing the advantages of the one-dimensional eight-level phase sampling scheme for the second holographic image.

[0035] Compared with other existing solutions, the present invention can realize hologram switching in a simpler way, and only manufactures one set of holographic metasurface unit structures, fully utilizing the structure without structural waste. Finally, a two-dimensional 8-level phase sampling scheme is proposed to construct a database, which can meet the 8-level phase setting before and after the phase change, and has significant advantages in imaging quality and image complexity.

[0036] S3. Based on the phase-size database and the pixel phase distribution of the two target holograms to be imaged, the unit structure size parameters that simultaneously meet the phase requirements of the two target holograms are matched for each pixel point to obtain multiple metasurface unit structures that meet the matching requirements; the multiple metasurface unit structures that meet the matching requirements are arranged and combined to form a single set of switchable holographic metasurface structures.

[0037] Two pictures are selected as holograms before and after the phase change. In this example, the pictures selected are "A" and "B" with white characters on a black background. Figure 6 (a) and (b) in the figure, the GS algorithm is used in MATLAB to extract the additional phase map of these two pictures. The results after pixel cutting are as follows Figure 6 (c) and (d) in the figure record additional phase information.

[0038] The super surface unit structure designed by the present invention is as follows Figure 4 As shown, the inner part is a cylinder made of phase change material GSST, and the outer part is a ring cylinder made of non-phase change material with a refractive index of 4.2. The period P of the unit structure is 900nm, and the height H of the nanocolumns of the entire unit structure is fixed at 1500nm. At a wavelength of 1550nm, the refractive index of GSST in the amorphous state is , when it changes into the crystalline state under external stimulation, the refractive index is Scan the cylindrical radius and outer radius of the ring cylinder of the designed unit structure in FDTD. The outer radius of the ring cylinder is fixed at 315nm, the ring cylinder radius scanning range is 205nm to 305nm, and the cylindrical radius scanning range is 50nm to 180nm. Use 1550nm linearly polarized plane wave excitation to numerically calculate the modulated complex electric field of the periodic unit structure array. The results are as follows Figure 5 As shown, Figure 5 (a) Figure 5 (b) are data diagrams showing the phase changes with the cylinder radius and the inner radius of the ring cylinder before and after the phase transition; Figure 5 (c) Figure 5 (d) are data graphs showing the changes in transmittance with the radius of the cylinder and the inner radius of the ring cylinder before and after the phase change.

[0039] like Figure 7 As shown, Figure 7 (a) Figure 7 (b) Figure 7 (c) Figure 7 (d) are the holographic imaging results with ±10nm, ±15nm, ±20nm, and ±25nm manufacturing tolerances. The results are as follows: Figure 5 The obtained results are interpolated into 200×200 data to provide more data for subsequent intelligent search work.

[0040] Table 1 Database chart based on phase-size data The obtained data were compared and analyzed on MATLAB, and an 8×8 phase-size database was obtained as shown in Table 1. The first number in the brackets is the cylinder radius, and the second number is the ring cylinder radius. The two constitute a size group. There are 64 size groups in the database. Among them, the unobtained parameters are used to represent. Based on the obtained 8×8 phase-size database, as shown in Table 1, and the phase distribution required for each pixel before and after the phase change, Figure 6 (a) Figure 6 (b) are the original images before and after phase change, Figure 6 (c) Figure 6 (d) are the additional phase images corresponding to the two original images respectively. Figure 6 (e), Figure 6 (f) is the imaging result of holographic imaging before and after phase change using the designed holographic metasurface. Figure 6 As shown in (c) and (d), the size of each unit structure on the metasurface is matched in sequence to make the metasurface. Holographic imaging is simulated on the metasurface, and the results are shown in Figure 6 (e) and (f) are the holograms before and after phase change, respectively.

[0041] Considering that the current manufacturing process cannot produce the required metasurface unit structure with accuracy, a manufacturing tolerance analysis is conducted on this case. After matching the corresponding cylinder and ring column sizes, a certain random manufacturing error is added, with error ranges of ±10nm, ±15nm, ±20nm, and ±25nm respectively. The imaging effect is as follows: Figure 7 As shown, it can be seen that this method has strong anti-noise performance.

[0042] Based on the same inventive concept, the present invention also provides a switchable holographic metasurface design device, comprising: A structural design module is used to establish a basic metasurface unit structure model; the basic metasurface unit structure model is a cylinder made of phase change material GSST inside and a ring column made of non-phase change material outside, and the two form a concentric cylindrical structure; A database establishment module is used to keep the outer radius of the circular cylinder of the basic metasurface unit structure model unchanged, simulate the combination structure of cylindrical radii of different sizes and inner radii of the circular cylinder, and obtain multiple metasurface unit structures of different sizes; set the phase change material GSST of the multiple metasurface unit structures of different sizes to amorphous and crystalline states, respectively, to obtain multiple amorphous metasurface unit structures and crystalline metasurface unit structures of different sizes; calculate the phase change and light transmittance corresponding to each amorphous metasurface unit structure and crystalline metasurface unit structure of different sizes; construct a phase-size data graph and a transmittance-size data graph before and after the phase change of the metasurface unit structure according to different phase changes and light transmittances; screen out size combinations that simultaneously meet the preset phase expected value and the preset transmittance threshold from the phase-size data graph and the transmittance-size data graph; and construct a phase-size database based on the size combinations that meet the conditions; The database application module is used to match the unit structure size parameters that simultaneously meet the phase requirements of the two target holograms for each pixel point based on the phase-size database and the pixel point phase distribution of the two target holograms to be imaged, thereby obtaining multiple metasurface unit structures that meet the matching requirements; and arranging and combining the multiple metasurface unit structures that meet the matching requirements to form a single set of switchable holographic metasurface structures.

[0043] The present invention also provides a computer device. At the hardware level, the computer device includes a processor, an internal bus, a network interface, memory, and non-volatile storage, and may also include other hardware required for the service. The processor reads the corresponding computer program from the non-volatile storage into the memory and then runs it to implement the switchable holographic metasurface design method provided above.

[0044] The present invention also provides a computer-readable storage medium, which stores a computer program, and the computer program can be used to execute the switchable holographic metasurface design method provided above.

[0045] For the specific definition of the switchable holographic metasurface design method computing system, please refer to the definition of the switchable holographic metasurface design method above, which will not be repeated here. The various modules in the above-mentioned switchable holographic metasurface design system can be implemented in whole or in part by software, hardware, and a combination thereof. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0046] The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. In addition, the above-mentioned embodiments only express several implementation methods of the present application, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of this application, several variations and improvements can be made, which all fall within the scope of protection of this application. Therefore, the scope of protection of the patent in this application shall be based on the attached claims.

[0047] It should be noted that the specific embodiments described above can enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. Therefore, although this specification and examples have described the present invention in detail, those skilled in the art should understand that the present invention can still be modified or replaced with equivalents; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention are included in the scope of protection of the patent for the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A method for designing a switchable holographic metasurface, characterized in that: The method comprises: Establishing a basic metasurface unit structure model; the interior of the basic metasurface unit structure model is a cylinder made of phase change material GSST, and the exterior is a ring column made of non-phase change material, and the two form a concentric cylindrical structure; Keeping the outer radius of the circular cylinder of the basic metasurface unit structure model unchanged, simulate the combined structures of cylindrical radii and inner radii of the circular cylinder of different sizes to obtain multiple metasurface unit structures of different sizes; The phase change material GSST of a plurality of metasurface unit structures of different sizes is set to an amorphous state and a crystalline state, respectively, to obtain a plurality of amorphous metasurface unit structures and crystalline metasurface unit structures of different sizes; the phase change amount and light transmittance corresponding to each amorphous metasurface unit structure and crystalline metasurface unit structure of different sizes are calculated respectively; according to the different phase change amounts and light transmittances, a phase-size data graph and a transmittance-size data graph of the metasurface unit structure before and after the phase change are constructed; from the phase-size data graph and the transmittance-size data graph, a size combination that simultaneously meets a preset phase expected value and a preset transmittance threshold is screened out; and a phase-size database is constructed based on the size combinations that meet the conditions; Based on the phase-size database and the pixel phase distribution of the two target holograms to be imaged, a unit structure size parameter that simultaneously meets the phase requirements of the two target holograms is matched for each pixel point to obtain multiple metasurface unit structures that meet the matching requirements; the multiple metasurface unit structures that meet the matching requirements are arranged and combined to form a single set of switchable holographic metasurface structures.

2. The method for designing a switchable holographic metasurface according to claim 1, wherein: The combined structure of the cylindrical radii and the inner radii of the annular cylinders of different sizes is simulated by the finite time-domain method (FDTD) to obtain a plurality of metasurface unit structures of different sizes.

3. The method for designing a switchable holographic metasurface according to claim 1, wherein: The simulation method includes simulating the combined structure of cylindrical radii and inner radii of circular ring columns of different sizes to obtain a plurality of supersurface unit structures of different sizes; and further includes performing numerical interpolation processing on the plurality of supersurface unit structures of different sizes, thereby setting the phase change material GSST of the plurality of supersurface unit structures of different sizes to an amorphous state and a crystalline state respectively.

4. The method for designing a switchable holographic metasurface according to claim 1, wherein: Using MATLAB data processing tools and a two-dimensional 8-level phase sampling algorithm, size combinations that simultaneously meet a preset phase expectation value and a preset transmittance threshold are screened out from the phase-size data graph and the transmittance-size data graph; a phase-size database is constructed based on the size combinations that meet the conditions.

5. The method for designing a switchable holographic metasurface according to claim 4, wherein: The phase-size database is an 8×8 phase-size database, containing 62 groups of valid data. The storage content of the phase-size database includes: the cylindrical radius of the metasurface unit structure, the inner radius of the annular cylinder, the phase before phase change, the phase after phase change, the transmittance before phase change, and the transmittance after phase change.

6. The method for designing a switchable holographic metasurface according to claim 1, wherein: The pixel point phase distribution of the two target holograms to be imaged is obtained by the GS algorithm, including: calculating the phase distribution of each pixel point of the two target holograms before and after the phase change by the GS algorithm, and matching the unit structure size parameters that simultaneously meet the phase requirements of the two target holograms for each pixel point based on the phase-size database and the phase distribution.

7. A switchable holographic metasurface design device, characterized in that: include: A structural design module is used to establish a basic metasurface unit structure model; the basic metasurface unit structure model is a cylinder made of phase change material GSST inside and a ring column made of non-phase change material outside, and the two form a concentric cylindrical structure; A database establishment module is used to keep the outer radius of the circular cylinder of the basic metasurface unit structure model unchanged, simulate the combination structure of cylindrical radii of different sizes and inner radii of the circular cylinder, and obtain multiple metasurface unit structures of different sizes; set the phase change material GSST of the multiple metasurface unit structures of different sizes to amorphous and crystalline states, respectively, to obtain multiple amorphous metasurface unit structures and crystalline metasurface unit structures of different sizes; calculate the phase change and light transmittance corresponding to each amorphous metasurface unit structure and crystalline metasurface unit structure of different sizes; construct a phase-size data graph and a transmittance-size data graph before and after the phase change of the metasurface unit structure according to different phase changes and light transmittances; screen out size combinations that simultaneously meet the preset phase expected value and the preset transmittance threshold from the phase-size data graph and the transmittance-size data graph; and construct a phase-size database based on the size combinations that meet the conditions; The database application module is used to match the unit structure size parameters that simultaneously meet the phase requirements of the two target holograms for each pixel point based on the phase-size database and the pixel point phase distribution of the two target holograms to be imaged, thereby obtaining multiple metasurface unit structures that meet the matching requirements; and arranging and combining the multiple metasurface unit structures that meet the matching requirements to form a single set of switchable holographic metasurface structures.

8. A computer device comprising a memory, a processor, and a computer program stored in the memory, wherein: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is loaded into a processor, it can execute the steps of the method according to any one of claims 1 to 6.

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