Holographic imaging design of dual-polarization multiplexing type reflection metasurface

Abstract

The invention discloses a holographic imaging design method for a dual-polarization multiplexing metasurface. The problem that a metasurface holographic unit structure achieved through an existing multi-layer medium cascade structure is complex is solved. Firstly, an anisotropic unit of the dual-polarization reflection metasurface is designed, the anisotropic unit comprises a top cross patch, a dielectric layer, a middle cross patch layer, a dielectric layer and a bottom all-metal layer in sequence, and the top layer and the middle layer are of a metal double-cross structure and have symmetry about the x axis and the y axis. By simulating a unit structure, a corresponding relation between the size of the unit structure and a reflection phase is established, and full-range phase modulation is realized; then, a metasurface is designed for a beam of dual-polarized electromagnetic waves, incident waves are vertically incident to the metasurface, and conditions needing to be met by the reflection phase of the metasurface are calculated; and the holographic imaging effect of the dual-polarization multiplexing metasurface reflection channel is further realized. The method has the advantages of being easy to design and process and the like, and is applied to the fields of information encryption, multi-channel information processing and the like.

Description

Technical Field

[0001] The present invention relates to a holographic imaging design method for a dual-polarization multiplexing metasurface, which can produce different holographic imaging effects for different incident polarization waves, relates to the microwave band, and belongs to the application technical fields of holographic display, polarization optics, and information encryption. Background Art

[0002] Polarization is one of the important information of electromagnetic waves. In the early stage, the multifunctional electromagnetic regulation of metasurfaces mainly focused on the information encoding of polarization element channels, and the dual-holographic technology was realized by encoding polarization information. Its potential uses in future optical applications, such as holographic imaging and optical data storage. In recent years, the electromagnetic regulation technology of subwavelength structures has stood out among many technologies due to its flexible design, precise electromagnetic modulation ability at the subwavelength scale, introduction of a certain gradient of phase mutation, and multi-parameter manipulation including phase, amplitude, and polarization, opening an alternative solution for compact holographic structures and high imaging quality. Through reasonable design, the reflective metasurface can achieve a wide phase coverage and high reflectivity, so it has been widely used in polarization converters, absorbers, etc. However, most artificial electromagnetic metasurfaces can only regulate electromagnetic waves in a single polarization direction, which limits their applications and the reflection performance of the metasurface. Therefore, in order to meet the growing demand for multifunctional and high-speed electromagnetic devices and improve the utilization rate of electromagnetic wave resources, it is very necessary and meaningful to integrate the polarization multiplexing manipulation function of electromagnetic waves into a single device, so as to realize holographic imaging of a polarization multiplexing metasurface. The polarization multiplexing metasurface hologram is sensitive to the incident polarization state, and different holographic images can be reconstructed by changing the polarization of the incident wave. The applications of polarization multiplexing metasurface devices in high-resolution image display, high-density information storage, information encryption, optical information processing, security anti-counterfeiting and other fields. Summary of the Invention

[0003] The purpose of the present invention is to meet the growing demand for multifunctional and high-speed electromagnetic devices and improve the utilization rate of electromagnetic wave resources, integrate the polarization multiplexing manipulation function of electromagnetic waves into a single device, so as to realize a holographic imaging design of a dual-polarization multiplexing metasurface, which can produce different holographic imaging effects when different polarization waves are incident, and the tunability of the reflection phase of different polarization wave incidents can be realized through this method. At the same frequency point, the coding unit realizes a wide range of reflection phase regulation and the phase change gradient basically remains unchanged, while ensuring a high reflectivity. Respectively, when the x-line polarized wave is incident vertically on the metasurface, the reflected co-polarized wave generates a hologram with a four-point convergence structure of a "diamond" shape. When the y-line polarized wave is incident vertically on the metasurface, the reflected co-polarized wave generates a hologram with a four-point convergence structure of a "square" shape.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention discloses a holographic imaging design method for a dual-polarization multiplexing metasurface, which solves the problem of the complex structure of the metasurface holographic unit realized by the existing multi-layer dielectric cascade structure. It includes a top cross patch, a dielectric layer, an intermediate cross patch layer, a dielectric layer, and a bottom full-metal layer in sequence. The top layer and the intermediate layer are in a metal "double cross" structure, which is symmetric about the x and y axes.

[0006] The holographic imaging design method for a dual-polarization multiplexing metasurface includes m×n periodically arranged phase mutation units, where both m and n are positive integers; and both m and n are 33.

[0007] In the holographic imaging design method for a dual-polarization multiplexing metasurface, the top cross patch, the intermediate cross patch layer, and the bottom full-metal layer are all copper layers, and the thickness of the copper sheet is 0.018 mm.

[0008] In the holographic imaging design method for a dual-polarization multiplexing metasurface, the unit structure is square, and the side length is p = 7 mm.

[0009] In the holographic imaging design method for a dual-polarization multiplexing metasurface, the thickness of the dielectric layer is 1 mm, the relative permittivity is 2.65, and the tangent value of the loss angle is 0.001.

[0010] In the holographic imaging design method for a dual-polarization multiplexing metasurface, the other fixed parameter values of the unit structure are: g = 0.4 mm.

[0011] In the holographic imaging design method for a dual-polarization multiplexing metasurface, the center of the working frequency of the metasurface is set to 15 GHz.

[0012] The high-efficiency metasurface unit with dual-polarization reflection phase regulation has a total of 16 basic unit states; under the irradiation of x-polarized or y-polarized electromagnetic waves, it can independently generate 4 different phase digital state encodings, and the 4 different phase digital state encodings should correspond to the sizes of the surface metal "cross" structure layers of 16 basic units.

[0013] Furthermore, the 4 digital state encodings are respectively "00", "01", "10", and "11", which respectively represent the reflection phase digital states under normal-incident electromagnetic waves.

[0014] In the holographic imaging design method for a dual-polarization multiplexing metasurface, when an x-line polarized wave is vertically incident on the metasurface, the reflected co-polarized wave generates a hologram with a four-point convergence of a "rhombus" structure.

[0015] The described holographic imaging design method of a dual-polarization multiplexing metasurface, where a y-linearly polarized wave is incident perpendicularly on the metasurface, and the co-polarized wave reflected therefrom generates a hologram with a four-point convergence having a "square" structure.

[0016] Advantageous effects:

[0017] The holographic imaging design method of a dual-polarization multiplexing metasurface described in the present invention analyzes and designs the metasurface from the perspective of digital coding, greatly simplifying the design process; by adjusting the size of the metal patches, full-phase modulation from 0 to 2π can be achieved, and the reflection efficiency is high, enabling encoding of different functional phases. Combining the encoded holographic phase distribution map with this multi-layer metasurface further realizes four holographic imaging reflection channels under two polarization incidences. The two functions are relatively independent, and the present invention is simple to process and easy to implement, relying only on simple metal patterns and being easy to fabricate in the microwave frequency band. Description of the drawings

[0018] Figure 1 It is a schematic structural diagram of the unit structure of the holographic imaging design of a dual-polarization multiplexing metasurface described in the present invention;

[0019] Figure 2 It is the size diagram corresponding to 16 different basic constituent units selected for the multi-layer metasurface of the holographic imaging design of a dual-polarization multiplexing metasurface described in the present invention.

[0020] Figure 3 It is the amplitude and phase modulation effects of 16 different basic constituent units selected for the multi-layer metasurface of the holographic imaging of a dual-polarization multiplexing metasurface described in the present invention for each channel. (a) Amplitude spectrum of the co-polarized polarization component of the reflected wave when an x-linearly polarized wave is incident perpendicularly on the metasurface. (b) Amplitude spectrum of the co-polarized polarization component of the reflected wave when a y-linearly polarized wave is incident perpendicularly on the metasurface. (c) Phase spectrum of the co-polarized polarization component of the reflected wave when an x-linearly polarized wave is incident perpendicularly on the metasurface. (d) Phase spectrum of the co-polarized polarization component of the reflected wave when a y-linearly polarized wave is incident perpendicularly on the metasurface.

[0021] Figure 4 It is the holographic simulation diagram (a) and holographic test diagram (b) of the co-polarized polarization reflected wave when an x-linearly polarized wave is incident perpendicularly on the multi-layer metasurface of the holographic imaging of a dual-polarization multiplexing metasurface described in the present invention, and the holographic simulation diagram (c) and holographic test diagram (d) of the co-polarized polarization reflected wave when a y-linearly polarized wave is incident perpendicularly on the multi-layer metasurface. Detailed implementation manners

[0022] For the convenience of those of ordinary skill in the art to understand and implement the present invention, the present invention will be further described in detail and depth below with reference to the accompanying drawings.

[0023] Specific Embodiment 1: In combination with Figure 1 Specifically illustrate this embodiment. The high-efficiency metasurface unit with dual-polarization reflection phase regulation described in this embodiment has a basic unit including a top cross patch, a dielectric layer, an intermediate cross patch layer, a dielectric layer, and a bottom full-metal layer. The top layer and the intermediate layer form a metal "double cross" structure, which is symmetric about the x and y axes. The thickness of the dielectric layer is 1 mm, the relative dielectric constant is 2.65, and the tangent value of the loss angle is 0.001. The top cross patch, the intermediate cross patch layer, and the bottom full-metal layer are all copper layers, and the thickness of the copper sheet is 0.018 mm.

[0024] Specific Embodiment 2: The unit structure is square, and the side length is p = 7 mm. The fixed values of the remaining parameters of the unit structure are: g = 0.4 mm. The center of the operating frequency of the metasurface is set to 15 GHz.

[0025] Specific Embodiment 3: In combination with Figure 2 Specifically illustrate this embodiment. Based on the CST simulation software, design the unit of the dual-polarization reflection metasurface, and establish the corresponding relationship between the unit structure size and the reflection phase. The high-efficiency metasurface unit with dual-polarization reflection phase regulation has a total of 16 basic unit states; under the irradiation of x-polarized or y-polarized electromagnetic waves, 4 different phase digital state encodings can be independently generated, as Figure 2 shown, the 4 different phase digital state encodings should correspond to the sizes of the surface metal "cross" structure layers of 16 basic units. Further, the 4 digital state encodings are respectively "00", "01", "10", and "11", which respectively represent the digital states of the reflection phase under the incident electromagnetic wave.

[0026] Specific Embodiment 4: In combination with Figure 3 Specifically illustrate this embodiment. By changing the different sizes of the unit structure, the responses of the unit to two orthogonal linearly polarized incident electromagnetic waves can be independently regulated, that is, the reflection phases of the unit to these two orthogonal linearly polarized incident electromagnetic waves can be independently controlled without interference, and the regulation range of the reflection phases of the unit to these two orthogonal linearly polarized incident waves is close to 2π. Figure 3 Shows the amplitude and phase modulation effects of the selected 16 different basic component units for each channel. Figure 3 (a) and 3(c) represent the amplitude spectrum and phase spectrum of the reflection co-polarization polarization component of the x-linearly polarized wave vertically incident on the metasurface. Figure 3(b) and 3(d) show the amplitude spectrum and phase spectrum of the co-polarization polarization component of the reflected wave when the y-line polarized wave is vertically incident on the metasurface. The results show that the unit structure has a high reflection efficiency regardless of whether the x-polarized wave or the y-polarized wave is incident. And the phase presents four polarization states.

[0027] Specific Embodiment 5: Combined Figure 4 Specifically describe this embodiment. The dual-polarization multiplexing metasurface described includes M×N periodically arranged phase mutation units, where both M and N are positive integers; and both M and N are 33. Figure 4 (a) and Figure 4 (b) show the holographic simulation diagram and test diagram of the co-polarization polarized reflected wave under the vertical incidence of the x-line polarized wave. The co-polarized wave reflected therefrom generates a hologram with four-point convergence having a "rhombus" structure. Figure 4 (c) and Figure 4 (d) show the holographic simulation diagram and test diagram of the co-polarization polarized reflected wave under the vertical incidence of the y-line polarized wave. The co-polarized wave reflected therefrom generates a hologram with four-point convergence having a "square" structure.

[0028] This embodiment can realize the independent control of electromagnetic waves in two reflection channels through phase encoding under the excitation of dual-polarization electromagnetic waves. By changing the size of the metasurface unit structure, different encoded metasurface holographic imaging is realized. The dual-polarization encoded metasurface proposed in this embodiment has good application prospects in the fields of beam control, beamforming, etc.

Claims

1. The present invention discloses a holographic imaging design method for a dual-polarization multiplexed metasurface, which solves the problem of the complex structure of the metasurface holographic unit realized by the existing multi-layer dielectric cascaded structure, and is characterized in that: It includes a top cross patch, a dielectric layer, a middle cross patch layer, a dielectric layer and a bottom full-metal layer in sequence. The top layer and the middle layer form a metal "double cross" structure, which is symmetric about the x and y axes.

2. The holographic imaging design method of a dual-polarization multiplexing metasurface according to claim 1, characterized in that: It includes m×n periodically arranged phase mutation units, where both m and n are positive integers; and both m and n are 33.

3. A holographic imaging design method for a dual-polarization multiplexing metasurface according to claim 1, characterized in that: The top cross patch, the middle cross patch layer, and the bottom full-metal layer are all copper layers, and the thickness of the copper sheet is 0.018 mm. The unit structure is square with a side length of p = 7 mm.

4. A holographic imaging design method for a dual-polarization multiplexing metasurface according to claim 1, characterized in that: The thickness of the dielectric layer is 1 mm, the relative dielectric constant is 2.65, and the tangent value of the loss angle is 0.

001.

5. A holographic imaging design method for a dual-polarization multiplexing metasurface according to claim 1, characterized in that: The fixed value of the remaining parameters of the unit structure is: g = 0.4 mm.

6. The holographic imaging design method of a dual-polarization multiplexing metasurface according to claim 1, characterized in that: The center of the operating frequency of the metasurface is set to 15 GHz.

7. A holographic imaging design method for a dual-polarization multiplexing metasurface according to claim 1, characterized in that: The high-efficiency metasurface unit with dual-polarization reflection phase regulation has 16 basic unit states in total; under the irradiation of x-polarized or y-polarized electromagnetic waves, it can independently generate digital state encodings with 4 different phases, and the 4 different-phase digital state encodings should correspond to the sizes of the surface metal "cross" structure layers of 16 basic units.

8. A holographic imaging design method for a dual-polarization multiplexing metasurface according to claim 1, characterized in that: The 4 digital state encodings are "00", "01", "10" and "11" respectively, which represent the digital states of the reflection phase under normal-incidence electromagnetic waves.

9. A holographic imaging design method for a dual-polarization multiplexing metasurface according to claims 1-8, characterized in that: When the x-line polarized wave is vertically incident on the metasurface, the co-polarized wave reflected by it generates a hologram with a four-point convergence of a "rhombus" structure.

10. A holographic imaging design method for a dual-polarization multiplexing metasurface according to claims 1-8, characterized in that: When the y-line polarized wave is vertically incident on the metasurface, the co-polarized wave reflected by it generates a hologram with a four-point convergence of a "square" structure.

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