A metasurface grating for wide-angle directional terahertz scattering

Abstract

The present invention discloses a metasurface grating for large-angle directional scattering of terahertz waves, including a metasurface grating, which includes a plurality of periodically arranged unit structures; the unit structure includes a base layer and a scattering layer, and the scattering layer is located on the top surface of the base layer; the scattering layer includes a first scattering layer and a second scattering layer, and the first scattering layer and the second scattering layer are respectively located on the top surface of the base layer, the outer periphery of the first scattering layer is tangent to the midline of the base layer, and the second scattering layer is not connected to the first scattering layer. The metasurface grating of the present invention has a large terahertz beam splitting angle and can deflect the light beam by nearly 70°. It is simple to use, has good effect, and is easy to produce.

Description

Technical Field

[0001] The patent of this invention relates to the field of terahertz light deflectors, specifically a metasurface grating for large-angle directional scattering of terahertz light. Background Art

[0002] Metasurfaces are planar metamaterials composed of single or multi-layer artificial structures that possess unique electromagnetic and / or other physical properties not found in nature. A class of electromagnetic metamaterials consisting of only one or a few periodically or aperiodically arranged unit structures in the direction of electromagnetic wave propagation can be called metasurfaces. Metasurfaces are not only fundamental to fundamental physics research but also possess considerable technological significance. They can locally modify optical properties within the subwavelength range, thereby promoting device miniaturization and system integration. Metasurfaces have demonstrated remarkable capabilities in locally manipulating the amplitude, phase, and polarization of light, spurring the development of numerous optical devices. Terahertz waves, electromagnetic waves with frequencies between 0.1 and 10 THz, overlap with millimeter waves in the long wavelength range and with infrared light in the short wavelength range. Therefore, they possess the penetrability of microwaves and the manipulability of light waves. Terahertz technology has broad applications in radar, remote sensing, homeland security, highly secure data communications and transmission, atmospheric and environmental monitoring, real-time bioinformatics extraction, and medical diagnostics. Therefore, terahertz research has significant application value for the national economy and national security.

[0003] On October 12, 2019, Patri's group proposed the Directed Waveguide Scattering Grating (DWSG). This all-dielectric scattering grating, composed of an integrated single waveguide scatterer, relies on interference between multiple modes excited by the incident wave to control the resulting emission. However, its small size makes it difficult to fabricate, and its narrow emission angle limits its application. Summary of the Invention

[0004] The purpose of the present invention is to provide a metasurface grating for terahertz large-angle directional scattering, so as to solve the problems that the directional waveguide scattering grating has a small structure, is not easy to prepare and has a small output angle. To achieve the above purpose, the present invention provides the following technical solutions: a metasurface grating for terahertz large-angle directional scattering, comprising a metasurface grating,

[0005] The metasurface grating includes a plurality of periodically arranged unit structures;

[0006] The unit structure includes a base layer and a scattering layer, wherein the scattering layer is located on the top surface of the base layer;

[0007] The scattering layer includes a first scattering layer and a second scattering layer. The first scattering layer and the second scattering layer are respectively located on the top surface of the base layer. The periphery of the first scattering layer is tangent to the center line of the base layer, and the second scattering layer is not connected to the first scattering layer.

[0008] Preferably, the base layer is a rectangular parallelepiped structure.

[0009] Preferably, the length, width and height of the base layer are 600 μm, 300 μm and 500 μm respectively.

[0010] Preferably, the first scattering layer and the second scattering layer 3 are cylindrical and rectangular structures respectively.

[0011] Preferably, the circular surface diameter of the first scattering layer is 190 μm and the height is 500 μm.

[0012] Preferably, the length, width and height of the second scattering layer are 125 μm, 300 μm and 500 μm respectively.

[0013] Preferably, the base layer, the first scattering layer and the second scattering layer are respectively made of silicon.

[0014] Preferably, the gap between the first scattering layer and the second scattering layer is 30 μm.

[0015] Preferably, the terahertz wave is vertically incident on the surface of the substrate layer. As the frequency of the terahertz wave changes, the angle of the outgoing light beam changes accordingly, which can cause the light beam to bend.

[0016] Preferably, when the terahertz wave frequency is 0.54, the maximum beam bending angle is reached, and the angle is 66.9.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The metasurface grating of the present invention has a large terahertz beam splitting angle and can deflect the light beam by nearly 70°.

[0019] 2. The periodic size of the metasurface grating unit of the present invention is at the micron level. Furthermore, the manufacturing method only requires traditional photolithography, making it easy to mass-produce.

[0020] 3. The metasurface grating of the present invention is simple to use and has good effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a three-dimensional structure diagram of the metasurface grating of the present invention;

[0022] Figure 2 A three-dimensional diagram of the metasurface grating unit structure of the present invention;

[0023] Figure 3 These are the 0th and 1st order diffraction spectra of the metasurface grating of the present invention at a frequency of 0.529-0.543 terahertz.

[0024] Figure 4It is the absolute value of the Poynting vector of the XZ section of the metasurface grating of the present invention at a frequency of 0.527 THz.

[0025] Figure 5 This is the far-field scattering image of the metasurface grating of the present invention at a frequency of 0.54 terahertz.

[0026] Figure 6 for Figure 5 Normalized intensity of far-field scattering in the plane where the center spot is located.

[0027] In the figure: 1, base layer; 2, first scattering layer; 3, second scattering layer. DETAILED DESCRIPTION

[0028] 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 embodiments described are only part of the embodiments of the invention patent, not all of the embodiments. Based on the embodiments in the invention patent, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention patent.

[0029] See also Figure 1-2 The present invention provides a metasurface grating for large-angle directional scattering of terahertz waves, including a metasurface grating, which includes a plurality of periodically arranged unit structures; the unit structure includes a base layer 1 and a scattering layer, and the scattering layer is located on the top surface of the base layer 1; the scattering layer includes a first scattering layer 2 and a second scattering layer 3, and the first scattering layer 2 and the second scattering layer 3 are respectively located on the top surface of the base layer 1, the outer periphery of the first scattering layer 2 is tangent to the midline of the base layer 1, and the second scattering layer 3 is not connected to the first scattering layer 2, and the specific gap is 30μm.

[0030] The base layer 1 is a rectangular parallelepiped structure, and the length, width and height of the base layer 1 are 600 μm, 300 μm and 500 μm respectively. The first scattering layer 2 and the second scattering layer 3 are cylindrical and rectangular parallelepiped structures respectively.

[0031] The first scattering layer 2 has a circular surface diameter of 190 μm and a height of 500 μm.

[0032] The length, width and height of the second scattering layer 3 are 125 μm, 300 μm and 500 μm respectively.

[0033] The materials of the base layer 1 , the first scattering layer 2 and the second scattering layer 3 are silicon, and the relative dielectric constant is 11.9.

[0034] The specific working process of this embodiment is as follows:

[0035] A beam of terahertz waves is incident vertically on the surface of the metasurface grating and is scattered after passing through the metasurface grating, such as Figure 3 As shown in the figure, in the range of 0.529-0.543 THz, the first-order diffraction intensity far exceeds that of the other orders, and the output angle changes with the frequency of the incident light.

[0036] like Figure 5 、 6 As shown in the figure, after vertically incident 0.54 terahertz wave, separated terahertz waves can be obtained in the free space where the outgoing wave propagates. Figure 5 Draw a sphere with a radius of 1m with the metasurface grating as the center. The intensity of the scattered wave received on the sphere is the far-field image. This image is a top-down view directly above the plane where the metasurface grating is located, so the spacing between the concentric circles gradually decreases from the inside to the outside. A -1 order scattered light spot can be seen at 66.9°. Figure 6 The horizontal axis is the angle, and the vertical axis is the normalized diffraction efficiency. The peak at 0° corresponds to the 0th order diffraction, and the peaks at +66.9° and -66.9° correspond to the 1st order diffraction.

[0037] Principle: The deflection of the emission angle is achieved through the scatterer 2. Figure 4 This is a cross-sectional view of the unit structure in the xz plane, showing the Poynting vector distribution. The energy propagation function, according to a universal definition, is obtained by integrating the energy flux density (the real part of the Poynting vector). We can consider the Poynting vector as the energy distribution. When the incident wave strikes the metasurface from substrate 1, guided and scattered modes are excited within scatterers 2 and 3. It can be observed that the majority of the energy distribution is in scatterer 2. This is because scatterer 3 is designed to have an asymmetric structure. Asymmetric structures have more design parameters to facilitate adjustment of the emission results. In scatterer 2, the energy distribution exhibits a regular point-like distribution, which is the result of the superposition of guided and scattered modes.

[0038] Figure 3 The horizontal axis is frequency, measured in terahertz, and the vertical axis is diffraction efficiency. The diffraction efficiency here is calculated relative to the incident wave intensity, so its maximum value is 1. m represents the order, and T represents the transmission. For mT = -1, this represents the -1 order transmission spectrum curve. The upper axis gives the corresponding output angle. According to the generalized Snell's law, the diffraction angle for that order can be calculated given the incident wavelength, incident angle, grating period, and diffraction order. In the figure, the incident wavelength is replaced by frequency, so the corresponding angle values on the left are larger than those on the right.

[0039] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A metasurface grating for terahertz large-angle directional scattering, comprising a metasurface grating, The metasurface grating includes a plurality of periodically arranged unit structures; The unit structure comprises a base layer (1) and a scattering layer, wherein the scattering layer is located on the top surface of the base layer (1); The scattering layer comprises a first scattering layer (2) and a second scattering layer (3), the first scattering layer (2) and the second scattering layer (3) being respectively located on the top surface of the base layer (1), the outer periphery of the first scattering layer (2) being tangent to the center line of the base layer (1), and the second scattering layer (3) not being in contact with the first scattering layer (2); The first scattering layer (2) and the second scattering layer (3) are cylindrical and rectangular parallelepiped structures respectively; The first scattering layer (2) has a circular surface diameter of 190 μm and a height of 500 μm; The second scattering layer (3) has a length, width and height of 125 μm, 300 μm and 500 μm respectively.

2. The metasurface grating for large-angle directional terahertz scattering according to claim 1, characterized in that: The base layer (1) is a rectangular parallelepiped structure.

3. The metasurface grating for large-angle directional terahertz scattering according to claim 2, characterized in that: The length, width and height of the base layer (1) are 600 μm, 300 μm and 500 μm respectively.

4. The metasurface grating for large-angle directional terahertz scattering according to claim 1, characterized in that: The materials of the base layer (1), the first scattering layer (2) and the second scattering layer (3) are respectively silicon, and the relative dielectric constant is 11.66-11.

9.

5. The metasurface grating for large-angle directional terahertz scattering according to claim 1, characterized in that: The gap between the first scattering layer (2) and the second scattering layer (3) is 30 μm.

6. The metasurface grating for large-angle directional terahertz scattering according to claim 1, characterized in that: The terahertz wave is vertically incident on the surface of the substrate layer. As the frequency of the terahertz wave changes, the angle of the outgoing light beam changes accordingly, which can cause the light beam to bend.

7. The metasurface grating for large-angle directional terahertz scattering according to claim 6, characterized in that: When the terahertz wave frequency is 0.54, the maximum beam bending angle is reached, which is 66.9°.

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