Transparent wave absorber metasurface structure and design method thereof

Abstract

The invention discloses a transparent wave absorber metasurface structure and a design method thereof, solves the problems that the transparent wave absorber metasurface structure is easy to imitate and low in design freedom degree, and belongs to the field of transparent wave absorber design. The method comprises the following steps: acquiring a binary coding matrix, selecting a broken line contour of 0 in the coding matrix to obtain a plurality of broken line contours, performing arrangement according to the sequence of the lengths of the broken line contours from large to small, selecting the first M broken line contours, and performing size normalization processing on the selected first M broken line contours to obtain a unit pattern; scaling the unit pattern according to the size required to be designed of the metasurface pattern, taking the scaled unit pattern as a reference, and generating a transparent wave absorber metasurface pattern by adopting rotational symmetry or radial symmetry; and generating a metasurface structure according to the transparent wave absorber metasurface pattern. According to the method, the metasurface is designed by adopting a complex pattern structure, so that the metasurface structure is difficult to effectively measure and evaluate the structure size performance, and meanwhile, the possibility that the design is copied is reduced.

Description

Technical Field

[0001] The invention relates to a transparent wave absorbing body super surface structure and a design method thereof, belonging to the field of transparent wave absorbing body design. Background Art

[0002] Transparent absorbers are a new type of material that is optically transparent and microwave absorbing. At the beginning of this century, researchers used transparent conductive films to construct classic electromagnetic absorption structures such as Salisbury screens and Jaumann absorbers, successfully making the structures both visible light transparent and microwave absorbing. However, these transparent absorber structures have problems such as narrow absorption bandwidth, large thickness, and low transmittance. Electromagnetic metasurfaces are artificial materials composed of subwavelength unit structures arranged in a specific way, which can regulate the basic physical characteristics of electromagnetic waves such as frequency, amplitude, phase and polarization. Research in recent years has shown that transparent absorbers designed with metasurfaces have been improved in key performance, but how to further improve electromagnetic absorption performance is limited by existing metasurface design methods.

[0003] The existing transparent absorber metasurface structure design mainly adopts the following two schemes. The first is a combination of simple metasurface patterns. The design of the metasurface structure is achieved by combining simple geometric structures within the unit. The second is to use a coding method, by dividing the metasurface unit into an N×N matrix, and controlling whether the matrix is ​​filled or not, to achieve the design of the metasurface structure. After designing the metasurface structure according to these two methods, the structure is electromagnetically simulated to extract parameters that need to be optimized, such as absorption bandwidth and absorption rate. And further fine-tune the structural parameters until the metasurface structure design is completed. However, this type of transparent absorber design method has limitations, low degrees of freedom, and the structure is easy to measure and evaluate the performance, which makes it easy to be imitated. Summary of the invention

[0004] In view of the problem that the existing transparent absorber supersurface structure is easy to be imitated and has a low degree of design freedom, the present invention provides a transparent absorber supersurface structure and a design method thereof.

[0005] The present invention provides a transparent absorber metasurface structure. The transparent absorber metasurface pattern is rotationally symmetric or radially symmetric based on a pattern. The pattern adopts one or more broken line contours of 0 or 1 in a binary coding matrix.

[0006] Preferably, the fold line profile is smoothed or unsmoothed.

[0007] Preferably, the transparent absorber supersurface structure includes three layers, the upper layer and the middle layer are the transparent absorber supersurface pattern and its complementary structure respectively, and the lower layer is a reflective layer.

[0008] The present invention also provides a method for designing a transparent absorber supersurface structure, comprising:

[0009] Obtain a binary encoding matrix, select a polyline contour of 0 or 1 in the encoding matrix, obtain multiple polyline contours, arrange them in descending order according to the length of the polyline contours, and select the first M polyline contours, where M is a positive integer;

[0010] Normalizing the size of the first M selected fold line contours to obtain a unit pattern;

[0011] The unit pattern is scaled according to the size required for the metasurface pattern design, and the scaled unit pattern is used as a reference to generate a transparent absorber metasurface pattern by adopting rotational symmetry or radial symmetry;

[0012] A metasurface structure is generated based on the metasurface pattern of a transparent absorber.

[0013] Preferably, the method further comprises using spline interpolation to smooth the first M fold line contours after size normalization, and discarding self-intersecting fold line contours to obtain a unit pattern.

[0014] Preferably, the method of the present application further comprises generating multiple hypersurface structures, and selecting the optimal hypersurface structure using an optimization algorithm:

[0015] S1. Establishing a population of absorbers, wherein each individual in the population of absorbers is a metasurface structure;

[0016] S2, assigning material properties to each individual, obtaining the electromagnetic absorption performance of each individual, and judging whether the electromagnetic absorption performance meets the requirements. If so, selecting a metasurface structure that meets the electromagnetic absorption performance requirements; if not, proceeding to S3;

[0017] S3. Generate individuals in the next generation population based on electromagnetic absorption performance and enter S2.

[0018] Preferably, in S2, the electromagnetic absorption performance of each individual is obtained according to electromagnetic simulation.

[0019] Preferably, in S2, the electromagnetic absorption performance of each individual is obtained according to the trained neural network, the input of the neural network is the parameters of the metasurface structure, and the output is the electromagnetic absorption performance of the corresponding metasurface structure.

[0020] Preferably, a genetic algorithm, an annealing algorithm or an ant colony algorithm is used to generate individuals in the next generation population according to electromagnetic absorption performance.

[0021] Preferably, the metasurface structure includes three layers, the upper layer and the middle layer are the transparent absorber metasurface pattern and its complementary structure, and the lower layer is a reflective layer. The beneficial effect of the present invention is that the present invention designs the absorber loss layer metasurface structure by generating a pattern, further broadening the design freedom of the absorber, and the structure designed by the method of the present invention has good broadband absorption performance. At the same time, due to the use of a complex structure metasurface, the structure is difficult to be effectively measured and the structural size performance is difficult to evaluate, and the possibility of the design being imitated is reduced. And the pattern structure design further improves the design freedom of the metasurface structure, which can be applied to the design of transparent absorbers with various bands and bandwidth requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the principle of the transparent absorber metasurface structure design method of the present invention;

[0023] Figure 2 for Figure 1 Schematic diagram of the absorption performance of the metasurface structure generated by the method;

[0024] Figure 3 It is a schematic diagram of the principle of the design method of the transparent absorber supersurface structure without adding contour softening treatment in the present invention;

[0025] Figure 4 for Figure 3 Schematic diagram of the absorption performance of the metasurface structure generated by the method;

[0026] Figure 5 It is a schematic diagram of the flow chart of the optimization algorithm of the present invention. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0029] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0030] The transparent absorber metasurface structure of this embodiment includes three layers, the upper layer and the middle layer are the transparent absorber metasurface pattern and its complementary structure, and the lower layer is the reflective layer. The transparent absorber metasurface pattern is rotationally symmetric or radially symmetric based on the pattern; the pattern uses one or more 0 or 1 broken line contours in the binary coding matrix. Whether the broken line contour is smooth or not is described in the specific implementation method 1 and the specific implementation method 2.

[0031] Specific implementation method 1. Figure 1 As shown, the method for designing a transparent absorber metasurface structure of this embodiment includes:

[0032] Step 1, code generation: obtain a binary code matrix; the dimension of the code matrix is ​​N×N, where 0 represents a white block and 1 represents a black block, where N>5, because when N is too small, a more complex contour cannot be generated;

[0033] Step 2, selecting a broken line contour: Select the broken line contour of 0 in the coding matrix to obtain multiple broken line contours, arrange them in descending order according to the length of the broken line contours, and select the first M broken line contours, where M is a positive integer; Figure 1 In the example, M=2; you can also select according to the polyline contour of 1;

[0034] Step 3: contour softening-size normalization: normalize the size of the first M selected polyline contours;

[0035] Normalize the first M selected polyline contours, that is, set the side lengths of the polyline contours along the x and y axes to 1;

[0036] The first M broken line contours after size normalization are smoothed by spline interpolation, and the self-intersecting broken line contours are discarded to obtain the pattern unit pattern; the side length of the smoothed contour is k*p / 4, where k is selected in the range of 0.5 to 1, and p is the structural period length.

[0037] Step 4: Hypersurface modeling rotational symmetry:

[0038] The unit pattern is scaled according to the size required for the metasurface pattern design, and the scaled unit pattern is used as a reference to generate a transparent absorber metasurface pattern with rotational symmetry or radial symmetry. Figure 1 is rotationally symmetric;

[0039] Step 5: Structural model:

[0040] The metasurface structure is generated according to the metasurface pattern of the transparent absorber. The metasurface structure has three layers. The upper structure and the middle structure are the metasurface pattern of the patterned transparent absorber and its complementary structure respectively, and the lower layer is the reflection layer.

[0041] like Figure 2 As shown, the structure designed in the first embodiment has good electromagnetic absorption performance and can achieve an absorption rate of more than 90% in the range of 4-20 GHz.

[0042] Specific implementation method 2: Figure 3 As shown, the method for designing a transparent absorber metasurface structure of this embodiment includes:

[0043] Step 1, code generation: obtain a binary code matrix; the dimension of the code matrix is ​​N×N, where 0 represents a white block and 1 represents a black block, where N>5, because when N is too small, a more complex contour cannot be generated;

[0044] Step 2, selecting a broken line contour: Select the broken line contour of 0 in the coding matrix to obtain multiple broken line contours, arrange them in descending order according to the length of the broken line contours, and select the first M broken line contours, where M is a positive integer; Figure 3 In M=3, there are blue line contour, yellow line contour and red line contour; you can also select according to the broken line contour of 1;

[0045] Step 3: Size normalization: normalize the size of the first M selected broken line contours to obtain the pattern unit pattern. Figure 3 There are three broken line contours in the figure, among which the yellow line is inside the blue line. The yellow line cannot be shown in the pattern unit pattern, so the yellow line contour can be discarded in this case.

[0046] Step 4: Hypersurface modeling rotational symmetry:

[0047] The unit pattern is scaled according to the size required for the metasurface pattern design, and the scaled unit pattern is used as a reference to generate a transparent absorber metasurface pattern with rotational symmetry or radial symmetry. Figure 3 is rotationally symmetric;

[0048] Step 5: Structural model:

[0049] The metasurface structure is generated according to the metasurface pattern of the transparent absorber. The metasurface structure has three layers. The upper structure and the middle structure are the metasurface pattern of the patterned transparent absorber and its complementary structure respectively, and the lower layer is the reflection layer.

[0050] The difference from the first embodiment is that the second embodiment does not need to be softened, and uses the broken line contour as the super surface, such as Figure 4 As shown, the structure designed in the second embodiment has good electromagnetic absorption performance, and can achieve an absorption rate of more than 90% in the range of 4-20GHz. In addition, since no softening method is used, the structural simulation does not need to divide fine grids, and the calculation time is shorter.

[0051] According to the transparent absorber super surface structure design method of the specific implementation mode 1 or the specific implementation mode 2, multiple super surface structures are generated, and the optimal super surface structure is selected by using the optimization algorithm, such as Figure 5 As shown, specifically including:

[0052] Step 1, establishing a population of absorbers, each individual in the population of absorbers is a generated metasurface structure;

[0053] Step 2: assign material properties to each individual, use electromagnetic simulation software or a neural network model to obtain the electromagnetic absorption performance of each individual, and determine whether the electromagnetic absorption performance meets the requirements. If so, select a metasurface structure that meets the electromagnetic absorption performance requirements. If not, proceed to step 3.

[0054] Step 3: Generate individuals in the next generation population based on electromagnetic absorption performance, and go to step 2. In this step, an optimization algorithm such as a genetic algorithm, an annealing algorithm or an ant colony algorithm is used to generate individuals in the next generation population based on electromagnetic absorption performance.

[0055] In the electromagnetic simulation software, it is necessary to preset the material of the structural base (blue part) and the material of the metasurface structure. The structural base can be made of materials such as PET, PVC, PDMS, TPU, and circuit boards. The metasurface structure uses conductive materials such as ITO film, metal film, metal oxide film, conductive silver paste, and silver nanowires. Its surface resistance ranges from 1-600Ω / sq. The process of using electromagnetic simulation software to obtain the electromagnetic absorption performance of each individual includes:

[0056] 1. Construct a model of the metasurface structure;

[0057] 2. Assign model structure material parameters;

[0058] 3. Set the incentive conditions of the model;

[0059] 4. Start electromagnetic simulation calculation, obtain the S parameters of the structure, process the S parameters, obtain the reflectivity and transmittance of the metasurface structure, and calculate the absorptivity based on the reflectivity and transmittance, that is, complete the calculation of the electromagnetic absorption performance.

[0060] The process of obtaining the electromagnetic absorption performance of each individual using the neural network model includes:

[0061] 1. Establish a neural network model to detect the absorption rate of the metasurface structure;

[0062] 2. Establish a training set, in which the parameters of the supersurface structure are used as input and the absorption rate of the corresponding supersurface structure is used as output;

[0063] 3. Use the training set to train the neural network model. When the neural network model converges, it is determined that the neural network model is well trained. Use the trained neural network to obtain the electromagnetic absorption performance of each individual.

[0064] This embodiment is a transparent absorber based on a pattern metastructure and a design method thereof. The absorber loss layer metasurface structure is designed by generating a pattern. In combination with the design method, an on-demand transparent absorber structure can be designed. This design strategy further broadens the design freedom of the absorber, and the designed structure has good broadband absorption performance. At the same time, due to the use of a complex structure metasurface, the structure is difficult to be effectively measured and the structural size performance is evaluated, which reduces the possibility of the design being copied.

[0065] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. A transparent absorber metasurface structure, characterized in that: The metasurface pattern of the transparent absorber is rotationally symmetric or radially symmetric based on the pattern; the pattern adopts one or more broken line contours of 0 or 1 in the binary coding matrix.

2. The transparent absorber metasurface structure according to claim 1, characterized in that: The fold line profile is smoothed or unsmoothed.

3. The transparent absorber metasurface structure according to claim 1, characterized in that: The transparent absorber super surface structure comprises three layers, the upper layer and the middle layer are the transparent absorber super surface pattern and its complementary structure respectively, and the lower layer is the reflection layer.

4. A method for designing a transparent absorber metasurface structure, characterized in that: include: Obtain a binary encoding matrix, select a polyline contour of 0 or 1 in the encoding matrix, obtain multiple polyline contours, arrange them in descending order according to the length of the polyline contours, and select the first M polyline contours, where M is a positive integer; Performing size normalization processing on the first M selected broken line contours to obtain a pattern; The pattern is scaled according to the size required for the metasurface pattern design, and the scaled pattern is used as a reference to generate a transparent absorber metasurface pattern by using rotational symmetry or radial symmetry; A metasurface structure is generated based on the metasurface pattern of a transparent absorber.

5. The method for designing a transparent absorber metasurface structure according to claim 1, characterized in that: The method further comprises using spline interpolation to smooth the first M broken line contours after the size normalization process, and discarding the broken line contours that are self-intersecting, so as to obtain a pattern.

6. The method for designing a transparent absorber supersurface structure according to claim 4 or 5, characterized in that: The method further includes generating a plurality of hypersurface structures and selecting an optimal hypersurface structure using an optimization algorithm: S1. Establishing a population of absorbers, wherein each individual in the population of absorbers is a metasurface structure; S2, assigning material properties to each individual, obtaining the electromagnetic absorption performance of each individual, and judging whether the electromagnetic absorption performance meets the requirements. If so, selecting a metasurface structure that meets the electromagnetic absorption performance requirements; if not, proceeding to S3; S3. Generate individuals in the next generation population based on electromagnetic absorption performance and enter S2.

7. The method for designing a transparent absorber metasurface structure according to claim 6, characterized in that: In S2, the electromagnetic absorption performance of each individual is obtained according to the electromagnetic simulation.

8. The method for designing a transparent absorber metasurface structure according to claim 6, wherein: In S2, the electromagnetic absorption performance of each individual is obtained according to the trained neural network, the input of the neural network is the parameters of the metasurface structure, and the output is the electromagnetic absorption performance of the corresponding metasurface structure.

9. The method for designing a transparent absorber metasurface structure according to claim 6, characterized in that: Genetic algorithm, annealing algorithm or ant colony algorithm is used to generate individuals in the next generation population according to electromagnetic absorption performance.

10. A transparent absorber metasurface structure design device, comprising a storage device, a processor, and a computer program stored in the storage device and executable on the processor, characterized in that: The processor executes the computer program to implement the steps of the method for designing a transparent absorber metasurface structure as described in any one of claims 1 to 7.

Images