Focused terahertz polarization controller

Abstract

The present invention discloses a focusing terahertz polarization controller. It is characterized in that it includes a terahertz wave incident end, a reflected terahertz wave output end, and a metasurface polarizer; wherein the metasurface polarizer is composed of N×N structural units periodically arranged on a plane perpendicular to the terahertz wave input direction, and N is a natural number; the array unit is obtained by rotating 4×4 notched concave metal microstructures counterclockwise with a step of α = 22.5°; the notched concave metal microstructure successively includes a metal notched concave on the top layer, a polyimide dielectric layer on the middle layer, and a bottom metal plate. The focusing terahertz polarization controller disclosed by the present invention has the characteristics of simple structure and easy processing, etc., and can generate different focal positions for terahertz waves with different polarization states incident, meeting the application requirements of the terahertz wave communication multiplexing system.

Description

Technical Field

[0001] The present invention relates to the field of terahertz waves, and particularly to a focusing terahertz polarization controller. Background Art

[0002] Terahertz waves refer to electromagnetic waves with frequencies in the range of 0.1 - 1.0 THz, which are located between microwaves and infrared rays in the electromagnetic spectrum, corresponding to the transition region from macroscopic classical theory to microscopic quantum theory and from the field of electronics to the field of photonics, and are a classic frontier interdisciplinary subject. For a quite long period, the terahertz band was considered a forbidden zone in the electromagnetic spectrum. Due to the lack of radiation sources and detectors for effectively generating and detecting terahertz waves, this terahertz band has been called the "terahertz gap" and has not attracted much attention in the scientific community. In recent years, with the rapid development of terahertz sources and detectors and the continuous research and development of terahertz functional devices, terahertz science and technology have achieved vigorous development, and its research has very broad application prospects in many fields such as nondestructive testing, security inspection, biomedical imaging, radar, and ultra-wideband communication.

[0003] The development of terahertz technology not only requires efficient terahertz wave sources and highly sensitive detectors, but also requires high-performance terahertz modulators, absorbers, filters and other related functional devices. Terahertz wave polarization devices are one of the core devices of terahertz systems and are important functional devices that can effectively regulate and change the polarization state of terahertz waves. Traditional terahertz wave polarizers are often realized by using the birefringence effect such as liquid crystals in crystals or polymers. However, this type of material only has the birefringence characteristic at certain fixed frequency points, resulting in the polarization of terahertz waves only at a single frequency point, which greatly limits the application range of such polarization devices. Therefore, it is very important to explore more efficient methods for terahertz wave polarization control.

[0004] The focusing terahertz polarization controller proposed by the present invention can perform focusing regulation on terahertz waves with different polarization states, has the characteristics of simple structure and easy processing, can generate different focal positions for the incidence of terahertz waves with different polarization states, and meets the application requirements of terahertz wave communication multiplexing systems. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a focusing terahertz polarization controller.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A focusing terahertz polarization controller. It is characterized in that it includes a terahertz wave incident end, a reflected terahertz wave output end, and a metasurface polarizer; wherein the metasurface polarizer is composed of N×N structural units periodically arranged on a plane perpendicular to the terahertz wave input direction, and N is a natural number; the array unit is obtained by rotating 4×4 notched concave metal microstructures counterclockwise with a step of α = 22.5°; the notched concave metal microstructure includes a top-layer metal notched concave, a middle-layer polyimide dielectric layer, and a bottom-layer metal plate from top to bottom.

[0008] The 16 microstructures in the above-mentioned structural unit are named A~P in sequence. The notched concave metal microstructure in microstructure A forms an angle of 22.5° with the x-axis; the notched concave metal microstructure in microstructure B forms an angle of 45° with the x-axis; the notched concave metal microstructure in microstructure C forms an angle of 67.5° with the x-axis; the notched concave metal microstructure in microstructure D forms an angle of 90° with the x-axis; the notched concave metal microstructure in microstructure E forms an angle of 112.5° with the x-axis; the notched concave metal microstructure in microstructure F forms an angle of 135° with the x-axis; the notched concave metal microstructure in microstructure G forms an angle of 157.5° with the x-axis; the notched concave metal microstructure in microstructure H forms an angle of 180° with the x-axis; the notched concave metal microstructure in microstructure I forms an angle of 202.5° with the x-axis; the notched concave metal microstructure in microstructure J forms an angle of 225° with the x-axis; the notched concave metal microstructure in microstructure K forms an angle of 247.5° with the x-axis; the notched concave metal microstructure in microstructure L forms an angle of 270° with the x-axis; the notched concave metal microstructure in microstructure M forms an angle of 292.5° with the x-axis; the notched concave metal microstructure in microstructure N forms an angle of 315° with the x-axis; the notched concave metal microstructure in microstructure O forms an angle of 337.5° with the x-axis; the notched concave metal microstructure in microstructure P forms an angle of 0° with the x-axis.

[0009] The specific parameters of each component in the above scheme can be preferably as follows:

[0010] Preferably, the structural unit is composed of 16 notched concave metal microstructures, and the 16 microstructures are respectively obtained by rotating counterclockwise with a step of the angle α = 22.5° formed by the notch of the concave metal microstructure and the x-axis.

[0011] Preferably, the notched concave metal microstructure is arranged in an "S" shape.

[0012] Preferably, the side length of the top-layer metal notched concave is 40~50μm, the line width is 2~8μm, the width of the left concave part is 10~20μm, the height is 5~15μm, the width of the right opening is 10~20μm, the thickness is 0.2~1.0μm, and the material is gold.

[0013] Preferably, the thickness of the polyimide dielectric layer is 35-45 μm.

[0014] Preferably, the thickness of the bottom metal plate is 0.2-1.0 μm, and the material is gold.

[0015] The focusing terahertz polarization controller of the present invention has the characteristics of simple structure and easy processing, and can generate different focal orientations for the incidence of terahertz waves with different polarization states, meeting the application requirements of the terahertz wave communication multiplexing system. Brief Description of the Drawings

[0016] Figure 1 It is a schematic diagram of the three-dimensional structure, unit structure, and the arrangement of the notched concave metal microstructures in an "S" shape of the focusing terahertz polarization controller;

[0017] Figure 2 It is a cross-sectional view of the unit with the notched concave metal microstructure;

[0018] Figure 3 It is a schematic diagram of the polarization control of the incident terahertz wave by the focusing terahertz polarization controller under the incidence of different polarized waves;

[0019] Figure 4 It is the focal position and energy distribution diagram on the xy plane at z = 900 μm directly above the focusing terahertz polarization controller under the incidence of left circularly polarized terahertz waves.

[0020] Figure 5 It is the energy distribution diagram on the xz plane at z = 900 μm directly above the focusing terahertz polarization controller under the incidence of left circularly polarized terahertz waves.

[0021] Figure 6 It is the focal position and energy distribution diagram on the xy plane at z = 900 μm directly above the focusing terahertz polarization controller under the incidence of right circularly polarized terahertz waves.

[0022] Figure 7 It is the energy distribution diagram on the xz plane at z = 900 μm directly above the focusing terahertz polarization controller under the incidence of right circularly polarized terahertz waves.

[0023] Figure 8 It is the focal position and energy distribution diagram of two focal points on the xy plane at z = 900 μm directly above the focusing terahertz polarization controller under the incidence of linearly polarized terahertz waves.

[0024] Figure 9 It is the energy distribution diagram on the xz plane at z = 900 μm directly above the focusing terahertz polarization controller under the incidence of linearly polarized terahertz waves.

[0025] Figure 10It is a schematic diagram of a 3×3 arrangement structure obtained by counterclockwise rotation of a notched concave metal microstructure with a step of α = 40ᵒ.

[0026] Figure 11 It is the focal position and energy distribution diagram on the xy plane at z = 900 μm directly above the Figure 9 structure under the incidence of left - circularly polarized terahertz waves.

[0027] Figure 12 It is the focal position and energy distribution diagram on the xy plane at z = 900 μm directly above the Figure 9 structure under the incidence of right - circularly polarized terahertz waves. Specific implementation manners

[0028] Figure 1 Shown are the three - dimensional structure, unit structure of the focusing terahertz polarization controller, and the schematic diagram of the notched concave metal microstructure arranged in an "S" shape. Figure 2 It is a cross - sectional view of the unit with a notched concave metal microstructure. Figure 3 It is a schematic diagram of the polarization control of the incident terahertz wave by the focusing terahertz polarization controller under the incidence of different polarized waves. The focusing terahertz polarization controller includes a terahertz wave incident end 1, a reflected terahertz wave output end 2, and a metasurface polarizer 3. Among them, the metasurface polarizer 3 consists of N×N structural units 4 arranged periodically on a plane perpendicular to the terahertz wave input direction, where N is a natural number. The array unit 4 is obtained by counterclockwise rotation of 4×4 notched concave metal microstructures 5 with a step of α = 22.5°. The notched concave metal microstructure 5 successively includes a top - layer metal notch concave 6, a middle - layer polyimide dielectric layer 7, and a bottom - layer metal plate 8 from top to bottom.

[0029] In this focusing terahertz polarization controller, the materials and parameters of each component can be adopted in the following ways:

[0030] The 16 microstructures in the structure unit 4 described above are sequentially named A to P. The notched concave metal microstructure 5 in microstructure A forms an angle of 22.5° with the x-axis; the notched concave metal microstructure 5 in microstructure B forms an angle of 45° with the x-axis; the notched concave metal microstructure 5 in microstructure C forms an angle of 67.5° with the x-axis; the notched concave metal microstructure 5 in microstructure D forms an angle of 90° with the x-axis; the notched concave metal microstructure 5 in microstructure E forms an angle of 112.5° with the x-axis; the notched concave metal microstructure 5 in microstructure F forms an angle of 135° with the x-axis; the notched concave metal microstructure 5 in microstructure G forms an angle of 157.5° with the x-axis; the notched concave metal microstructure 5 in microstructure H forms an angle of 180° with the x-axis; the notched concave metal microstructure 5 in microstructure I forms an angle of 202.5° with the x-axis; the notched concave metal microstructure 5 in microstructure J forms an angle of 225° with the x-axis; the notched concave metal microstructure 5 in microstructure K forms an angle of 247.5° with the x-axis; the notched concave metal microstructure 5 in microstructure L forms an angle of 270° with the x-axis; the notched concave metal microstructure 5 in microstructure M forms an angle of 292.5° with the x-axis; the notched concave metal microstructure 5 in microstructure N forms an angle of 315° with the x-axis; the notched concave metal microstructure 5 in microstructure O forms an angle of 337.5° with the x-axis; the notched concave metal microstructure 5 in microstructure P forms an angle of 0° with the x-axis.

[0031] The structure unit 4 described above is composed of 16 notched concave metal microstructures 5. The 16 microstructures are obtained by rotating counterclockwise with a step of the notch of the concave metal microstructure forming an angle α = 22.5° with the x-axis. The notched concave metal microstructures 5 are arranged in an "S" shape. The side length of the top metal notch concave 6 is 40 - 50 μm, the line width is 2 - 8 μm, the width of the left concave part is 10 - 20 μm, the height is 5 - 15 μm, the width of the right opening is 10 - 20 μm, the thickness is 0.2 - 1.0 μm, and the material is gold. The thickness of the polyimide dielectric layer 7 is 35 - 45 μm. The thickness of the bottom metal plate 8 is 0.2 - 1.0 μm, and the material is gold.

[0032] The following is based on this focusing terahertz polarization controller, and its specific technical effects are described through examples.

[0033] Example 1

[0034] In this example, the structure of the focusing terahertz polarization controller and the shapes of its various components are as described above, so they will not be elaborated here. However, the specific parameters of each component are as follows:

[0035] The structural unit 4 is composed of 16 notched concave metal microstructures 5. The 16 microstructures are obtained by rotating counterclockwise with the notch of the concave metal microstructure making an angle α = 22.5° with the x-axis as the step. The notched concave metal microstructures 5 are arranged in an "S" shape. The side length of the top metal notched concave 6 is 50 μm, the line width is 5 μm, the width of the left concave part is 20 μm, the height is 10 μm, the width of the right opening is 10 μm, and the thickness is 1.0 μm. The material is gold. The polyimide dielectric layer 7 has a thickness of 40 μm. The bottom metal plate 8 has a thickness of 0.2 μm, and the material is gold.

[0036] The terahertz wave signal is input from the input end 1 and output from the reflected terahertz wave output end 2 through the action of a focusing terahertz polarization controller. When the left-circularly polarized terahertz wave is incident from the input end 1, the terahertz wave with a frequency of 1 THz is reflected by the metasurface polarizer 3 and output from the reflected terahertz wave output end 2. At a position z = 900 μm directly above the focusing terahertz polarization controller, a focus appears on the positive half-axis of the x-axis in the xy plane, 300 μm away from the origin, as Figure 4 shown. Figure 5 is the energy distribution diagram in the xz plane at a position z = 900 μm directly above the focusing terahertz polarization controller under the incidence of the left-circularly polarized terahertz wave. A focus can be seen on the right side of the xz plane. When the right-circularly polarized terahertz wave is incident from the input end 1, the terahertz wave with a frequency of 1 THz is reflected by the metasurface polarizer 3 and output from the reflected terahertz wave output end 2. At a position z = 900 μm directly above the metasurface polarizer 3, a focus appears on the negative half-axis of the x-axis in the xy plane, 300 μm away from the origin, as Figure 6 shown. Figure 7 is the energy distribution diagram in the xz plane at a position z = 900 μm directly above the focusing terahertz polarization controller under the incidence of the right-circularly polarized terahertz wave. A focus can be seen on the left side of the xz plane. When the linearly polarized terahertz wave with a frequency of 1 THz is incident, the reflected terahertz wave is output from the reflected terahertz wave output end 2. At a position z = 900 μm directly above the metasurface polarizer 3, two foci are formed on both sides of the origin of the x-axis in the xy plane, with a spacing of 600 μm, as Figure 8 shown. Figure 9 is the energy distribution diagram in the xz plane at a position z = 900 μm directly above the focusing terahertz polarization controller under the incidence of the linearly polarized terahertz wave. One focus can be seen on each of the left and right sides of the xz plane. From Figures 4 to 9 it can be seen that when terahertz waves with different polarizations are incident, after the action of the focusing terahertz polarization controller of the present invention, the positions of the foci generated by the reflected terahertz waves are different, indicating that the device can perform focusing regulation on terahertz waves with different polarization states.

[0037] Embodiment 2

[0038] In this embodiment, the structural unit 4 of the focusing terahertz polarization controller is composed of 3×3 notched concave metal microstructures 5, and the notched concave metal microstructures 5 are obtained by rotating counterclockwise with a step of α = 40°, as Figure 10 shown. The terahertz wave signal is input from the input end 1, and after being acted on by the focusing terahertz polarization controller, it is output from the reflected terahertz wave output end 2. When the left circularly polarized terahertz wave is incident from the input end 1, the terahertz wave with a frequency of 1 THz is reflected by the metasurface polarizer 3 and output from the reflected terahertz wave output end 2. At z = 900 μm directly above the array concentrator 3, no focal point is found in the xy plane (as Figure 11 shown), indicating that the reflected terahertz wave is not focused. When the right circularly polarized terahertz wave with a frequency of 1 THz is incident on the metasurface polarizer 3, the reflected terahertz wave is output from the reflected terahertz wave output end 2. At z = 900 μm directly above the array concentrator 3, no focal point is found in the xy plane (as Figure 12 shown), which also indicates that the reflected terahertz wave is not focused. This embodiment shows that without arranging the structure according to the design of the present invention, the device cannot achieve focusing control of terahertz waves with different polarizations incident.

Claims

1. A focusing terahertz polarization controller, characterized in that It includes a terahertz wave incident end (1), a reflected terahertz wave output end (2), and a metasurface polarizer (3); wherein the metasurface polarizer (3) is composed of N×N structural units (4) periodically arranged on a plane perpendicular to the terahertz wave input direction, and N is a natural number; The structural unit (4) is obtained by rotating 4×4 notched concave metal microstructures (5) counterclockwise with a step of α = 22.5°; The notched concave metal microstructure (5) successively includes a top-layer metal notch concave (6), a middle-layer polyimide dielectric layer (7), and a bottom-layer metal plate (8) from top to bottom; The 16 microstructures in the structural unit (4) are successively named A to P and arranged in an "S" shape; the notched concave metal microstructure (5) in microstructure (A) forms an angle of 22.5° with the x-axis; the notched concave metal microstructure (5) in microstructure (B) forms an angle of 45° with the x-axis; the notched concave metal microstructure (5) in microstructure (C) forms an angle of 67.5° with the x-axis; the notched concave metal microstructure (5) in microstructure (D) forms an angle of 90° with the x-axis; the notched concave metal microstructure (5) in microstructure (E) forms an angle of 112.5° with the x-axis; the notched concave metal microstructure (5) in microstructure (F) forms an angle of 135° with the x-axis; the notched concave metal microstructure (5) in microstructure (G) forms an angle of 157.5° with the x-axis; the notched concave metal microstructure (5) in microstructure (H) forms an angle of 180° with the x-axis; the notched concave metal microstructure (5) in microstructure (I) forms an angle of 202.5° with the x-axis; the notched concave metal microstructure (5) in microstructure (J) forms an angle of 225° with the x-axis; the notched concave metal microstructure (5) in microstructure (K) forms an angle of 247.5° with the x-axis; the notched concave metal microstructure (5) in microstructure (L) forms an angle of 270° with the x-axis; the notched concave metal microstructure (5) in microstructure (M) forms an angle of 292.5° with the x-axis; the notched concave metal microstructure (5) in microstructure (N) forms an angle of 315° with the x-axis; the notched concave metal microstructure (5) in microstructure (O) forms an angle of 337.5° with the x-axis; the notched concave metal microstructure (5) in microstructure (P) forms an angle of 0° with the x-axis.

2. The focusing terahertz polarization controller according to claim 1, wherein The structural unit (4) is composed of 16 notched concave metal microstructures (5), and the 16 microstructures are respectively obtained by rotating counterclockwise with a step of the notch of the concave metal microstructure forming an angle of α = 22.5° with the x-axis.

3. The focusing terahertz polarization controller according to claim 1, wherein The side length of the top-layer metal notch concave (6) is 40 - 50 μm, the line width is 2 - 8 μm, the width of the left concave part is 10 - 20 μm, the height is 5 - 15 μm, the width of the right opening is 10 - 20 μm, the thickness is 0.2 - 1.0 μm, and the material is gold.

4. A focusing terahertz polarization controller according to claim 1, characterized in that The thickness of the polyimide dielectric layer (7) is 35 - 45 μm.

5. The focusing terahertz polarization controller according to claim 1, wherein The thickness of the bottom-layer metal plate (8) is 0.2 - 1.0 μm, and the material is gold.

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