Device for generating non-Ermith singular point and realizing beam deflection

Abstract

The invention discloses a device for generating a non-Ermith singular point and realizing beam deflection, and relates to the technical field of terahertz artificial electromagnetic materials and terahertz wave beam deflection, in particular to a periodic digging hole arrangement array for realizing the singular point, a silicon dielectric plate serving as a singular point material, and a metal dielectric plate serving as a metal dielectric plate serving as a metal dielectric plate serving as a metal dielectric plate. 360-degree phase coverage can be realized by selecting different parameter units near the singular point, so that effective beam deflection is realized. The structure is simple, the preparation process is simple, the terahertz non-Ermith singular point is realized, the means of the existing terahertz non-Ermith singular point is enriched, and through the phase gradient arrangement of the generalized Snell law, the beam deflection of the transmission terahertz wave can be realized, the terahertz wavefront shaping can be realized, and the terahertz non-Ermith singular point can be obtained. And the terahertz high-sensitivity sensing is realized, and the application prospect is relatively good.

Description

Technical Field

[0001] The invention relates to the technical field of terahertz artificial electromagnetic materials and terahertz wave beam deflection, and in particular to a device for generating non-Hermitian singular points and realizing beam deflection. Background Art

[0002] Metasurfaces are artificial materials composed of periodic arrays of subwavelength arrays of Wiener structures that can achieve arbitrary desired electromagnetic wavefront control. In recent years, with the rapid development of terahertz technology, the application of metasurfaces in the terahertz field has also attracted widespread attention. With its arbitrary wavefront manipulation capability, metasurfaces have shown great potential in terahertz imaging, sensing, and communication. In essence, a metasurface is an open system that continuously exchanges and transfers energy between external excitation or radiation fields and subwavelength periodic structures. Unlike ideal closed systems, open systems undergo phase transitions with spatial and temporal inversion symmetry at singular points (EPs), resulting in complex scattering and resonance phenomena associated with singular points. These phenomena can be explained using scattering matrices and Hamiltonian descriptions. Singular points appear in various situations, such as zero reflection, perfect absorption, and bound states in the continuous spectrum, leading to unidirectional transmission or reflection, single-mode laser operation, and abnormal sensitivity to perturbations. By changing the geometry of the micro-nanostructure to adjust the value of the complex coefficient, the reflection or transmission of light can be manipulated.

[0003] At present, the method to obtain singular points in terahertz metasurfaces is to obtain them through transmission matrices including transmission or reflection matrices, but the current process and measurement errors make it difficult to directly obtain singular points. In addition, the traditional design of metasurfaces is based on three mechanisms: resonance phase, propagation phase, and geometric phase from angle. However, the metasurface structure envisioned in this study does not lead to a complete 360-degree phase accumulation in any loop in all parameter spaces. Summary of the invention

[0004] Purpose of the invention: In view of the above-mentioned problems and shortcomings of the current prior art, the present invention proposes a device for generating non-Hermitian singular points and realizing beam deflection, so as to overcome the above-mentioned technical problems existing in the existing related technology.

[0005] Technical Solution

[0006] To achieve the above-mentioned purpose of the invention, the first technical solution adopted by the present invention is a device for generating non-Hermitian singularities and realizing beam deflection, wherein the device includes a metasurface, wherein the metasurface includes a single-layer ultra-thin silicon wafer, and the single-layer ultra-thin silicon wafer has a periodic hole array.

[0007] Furthermore, in order to simplify the device structure, the thickness of the single-layer ultra-thin silicon wafer is 120 microns, the radius of the hole is 70.4 microns, and the period is 230 microns.

[0008] Furthermore, the parameters of the non-Hermitian singular points are determined by eigenmode analysis.

[0009] Furthermore, the non-Hermitian singular points are generated in the wave vector space far away from the high symmetry points.

[0010] The second technical solution provided by the present invention is a method for preparing the device as described above, comprising the following steps:

[0011] (1) thinning a single-layer silicon wafer to form a single-layer ultra-thin silicon wafer, and ultrasonically cleaning the surface of the single-layer ultra-thin silicon wafer with acetone, ethanol and water in sequence;

[0012] (2) spin coating the photoresist and drying it to obtain a single-layer ultra-thin silicon wafer after the spin coating of the photoresist, aligning the single-layer ultra-thin silicon wafer with the mask using a photolithography machine for exposure, developing it with a positive photoresist developer after the exposure is completed, and observing the photolithography development effect under a microscope;

[0013] (3) A periodic hole pattern is prepared on a single-layer ultra-thin silicon wafer after photolithography development using a deep silicon etching method, wherein the etching depth is equal to the thickness of the silicon wafer. After the etching is completed, the surface of the single-layer ultra-thin silicon wafer is cleaned again with acetone, ethanol and water to obtain an ultra-surface.

[0014] Furthermore, the thickness of the single-layer ultra-thin silicon wafer is 120 microns.

[0015] Beneficial Effects

[0016] The present invention proposes a device for generating non-Hermitian singular points and realizing beam deflection. Compared with previous results, a simple and easy-to-implement hole-digging structure is adopted to directly realize the simultaneous merging of the real and imaginary parts of the complex frequency space. At the same time, the topological phase based on the singular point can fully cover the phase of 360 degrees. The singular point and beam deflection device can be realized through a simple preparation process. The subsequent scalability is strong, and it has good application prospects in the field of beam control. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A three-dimensional view and a top view of the singular point unit structure of the terahertz metamaterial of the present invention;

[0018] Figure 2 (a) and (b) are respectively the real and imaginary parts of the intrinsic complex frequency of the structure designed by the present invention in the wave vector space;

[0019] Figure 3 Phase diagrams of four different radii selected near a singular point provided by the present invention;

[0020] Figure 4 The transmission electric field diagram of the transmitted terahertz wave provided by the present invention produces a deflection angle of 36.5 degrees DETAILED DESCRIPTION

[0021] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. Note that it should be understood that these embodiments are only for the purpose of more clearly and in detail describing the present invention and should not be understood as being used to limit the present invention in any form. After reading the present invention, the modification of various equivalent forms of the present invention by those skilled in the art all falls within the scope defined by the appended claims of the present application.

[0022] 1. Design of non-Hermitian singularity metasurface structural unit

[0023] In order to design a new type of terahertz non-Hermitian singular point structure, the present invention uses the finite element method to perform a large number of electromagnetic simulations in the wave vector space. Compared with the traditional method of obtaining terahertz singular points, we only need the result of a single electromagnetic polarization, and our unit structure is simple, and the parameter space only has three parameters: period, thickness and radius, such as Figure 1 As shown in the figure, through the eigenmode analysis of electromagnetic simulation, we determined that the parameter thickness is 120 microns, the specific parameters of the hole circle are radius r = 70.4 microns, and period p = 230 microns. Its real and imaginary parts are simultaneously degenerate at ±0.023 in the wave vector space, as shown in the figure. Figure 2 As shown in (a) and (b), it means that the system is at the EP point, and its operating frequency is found to be about 0.56 THz. In the real number space, through the formula k2π / p=sinθω / c, where k represents the in-plane wave vector, p is the unit period, θ represents the wave vector of the incident wave, ω is the frequency of the incident wave, and c is the speed of light. Therefore, it can be determined that the terahertz wave needs to be incident at an angle of 1.5 degrees to stimulate the generation of singular points. This also reflects another advantage of the design of the present invention, that is, the present invention is characterized in the wave vector space. Compared with other schemes, the present invention only needs one sample, and the singular point can be achieved by changing the incident angle.

[0024] 2. Devices with non-Hermitian singularities and beam steering based on the topological phase near them

[0025] According to the parameters of the non-Hermitian terahertz singular point determined by the electromagnetic field simulation software, two radii are selected before and after the terahertz singular point, such as Figure 3As shown in the figure, the phase results under different radius parameters. The results show that the phase under different radius parameters can achieve 360-degree coverage at 0.56THz, and then the radii under the four parameters are arranged in a gradient to form an array of terahertz beam deflection devices. When the terahertz wave is incident at an oblique angle of 1.5 degrees, it can be emitted at a certain angle after being adjusted by the beam deflection device. According to the formula where θ d is the deflection angle, λ is the operating wavelength, represents the phase gradient, so the calculated deflection angle is 35.6 degrees, as Figure 4 shown.

[0026] 3. Preparation method of a device for realizing beam deflection based on a non-Hermitian singular point and a topological phase near the singular point

[0027] The specific implementation includes the following steps:

[0028] (1) After the silicon wafer is thinned to 120 μm, the surface of the single-layer ultra-thin silicon wafer is ultrasonically cleaned with acetone, ethanol and water in sequence, with each cleaning time being five minutes;

[0029] (2) After cleaning, spin-coating photoresist and drying to obtain a single-layer ultra-thin silicon wafer after spin-coating photoresist, aligning the single-layer ultra-thin silicon wafer with the mask using a photolithography machine for exposure, developing with a positive photoresist developer after exposure, and observing the photolithography development effect under a microscope;

[0030] (3) A periodic hole pattern is prepared on the silicon wafer after photolithography using a deep silicon etching method. The etching depth is the thickness of the silicon wafer. After the etching is completed, the surface of the single-layer ultra-thin silicon wafer is cleaned again with acetone, ethanol and water to obtain an ultra-surface. The preparation is completed.

[0031] In summary, with the help of the above-mentioned technical solution of the present invention, the device and preparation method for generating non-Hermitian singular points and realizing beam deflection provided by the present invention adopt a simple and easy-to-implement hole-digging structure, compared with the acquisition of traditional terahertz singular points, and directly realize the simultaneous merging of the real and imaginary parts of the complex frequency space. At the same time, the topological phase based on the singular point can fully cover the phase of 360 degrees. The singular point and beam deflection device can be simply realized through a simple preparation process. It has strong subsequent scalability and has good application prospects in the field of beam control.

Claims

1. A device for generating non-Hermitian singular points and realizing beam deflection, characterized in that: The device comprises a super surface, the super surface comprises a single-layer ultra-thin silicon wafer, and a hole array with a periodic structure is arranged on the single-layer ultra-thin silicon wafer.

2. The device for generating non-Hermitian singular points and realizing beam deflection according to claim 1, characterized in that: The thickness of the single-layer ultra-thin silicon wafer is 120 microns, the radius of the hole is 70.4 microns, and the period is 230 microns.

3. The device for generating a non-Hermitian singular point and realizing beam deflection based on a topological phase near the singular point according to claim 1, characterized in that: The parameters of the non-Hermitian singular points are determined by eigenmode analysis.

4. The device for generating non-Hermitian singular points and realizing beam deflection according to claim 1, characterized in that: The non-Hermitian singular points are generated in the wave vector space far away from the high symmetry points.

5. The device for generating non-Hermitian singular points and realizing beam deflection according to claim 1, characterized in that: The phase of the radius parameter selected near the non-Hermitian singular point conforms to the linear gradient change and satisfies the 360-degree phase change.

6. A method for preparing the device as claimed in claim 1, characterized in that: The steps include: (1) thinning a single-layer silicon wafer to form a single-layer ultra-thin silicon wafer, and ultrasonically cleaning the surface of the single-layer ultra-thin silicon wafer with acetone, ethanol and water in sequence; (2) spin coating the photoresist and drying it to obtain a single-layer ultra-thin silicon wafer after the spin coating of the photoresist, aligning the single-layer ultra-thin silicon wafer with the mask using a photolithography machine for exposure, developing it with a positive photoresist developer after the exposure is completed, and observing the photolithography development effect under a microscope; (3) A periodic hole pattern is prepared on a single-layer ultra-thin silicon wafer after photolithography development using a deep silicon etching method, wherein the etching depth is equal to the thickness of the silicon wafer. After the etching is completed, the surface of the single-layer ultra-thin silicon wafer is cleaned again with acetone, ethanol and water to obtain an ultra-surface.

7. The preparation method according to claim 6, characterized in that: The thickness of the single-layer ultra-thin silicon wafer is 120 microns.

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