Terahertz polarization-maintaining vortex controller with twin rectangular graphene structure

Abstract

The invention discloses a terahertz polarization-maintaining vortex controller with a twin rectangular graphene structure, and belongs to the field of terahertz devices. The terahertz polarization-maintaining vortex controller is composed of a twinborn rectangular graphene layer, a silicon dioxide dielectric layer and a metal matrix layer, the conductivity of the terahertz polarization-maintaining vortex controller can be changed by changing the Fermi level of graphene, unit structures with different phases are generated, the unit structures are arranged in different modes, and the performance of the terahertz polarization-maintaining vortex controller is improved. Terahertz vortex wave beams with different topological charges and angle beam splitting are achieved, and the polarization state of the vortex wave beams is kept consistent with the polarization state of incident terahertz waves. The terahertz polarization-maintaining vortex controller disclosed by the invention has the advantages of simple structure, multiple functions, strong controllability and the like, and has a very wide application prospect in the terahertz communication field.

Description

Technical Field

[0001] The invention relates to the field of terahertz functional devices, and in particular to a terahertz polarization-maintaining vortex controller with a twin rectangular graphene structure. Background Art

[0002] Vortex waves are unique wave beams with a spiral phase structure and annular amplitude field. The orbital angular momentum (OAM) they carry has infinite eigenstates. Each orbital angular momentum state can be determined by the topological charge, which can take any integer value. The infinity of orbital angular momentum modes and the orthogonality between modes provide a new degree of freedom for the modulation and information carrying of electromagnetic waves. In the terahertz frequency range, the use of orbital angular momentum technology can achieve infinite signal transmission. Therefore, the realization of vortex wave control in terahertz is expected to greatly improve the bandwidth and capacity of wireless communication systems, and has great potential in the field of high-speed wireless communication. Vortex waves carrying orbital angular momentum have attracted widespread attention from researchers at home and abroad. At present, the methods for generating vortex waves mainly include the spiral phase plate method, the spiral reflector method, and the circular array antenna method. However, the above-mentioned spiral phase plate method, the reflector method, and the circular array antenna method have the characteristics of large device structure volume, complex system, high preparation difficulty, and high production cost for generating orbital angular momentum vortex waves, which are not applicable in the terahertz wave frequency range. In addition, once such devices are fabricated, the topological charge of their vortex waves is also determined and cannot be adjusted, which greatly limits the application potential of vortex wave beams. Therefore, the development of vortex wave generators with small size and adjustable state is of great significance to the application expansion of vortex waves in cutting-edge fields.

[0003] The present invention proposes a new terahertz polarization-maintaining vortex controller structure, which has twin rectangular graphene of the same size, and generates vortex waves carrying orbital angular momentum for incident terahertz waves. The unique electrical properties of the graphene metasurface are utilized to adjust the size of the graphene Fermi level to obtain different reflection phases, thereby achieving adjustability of the vortex beam and being able to make flexible adjustments according to actual needs. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the existing terahertz vortex polarization-maintaining control cannot be achieved. A twin rectangular graphene metasurface structure is designed and used, and the twin rectangular graphene metasurface arrangement is combined with the adjustment of the graphene Fermi level to achieve the control of the terahertz vortex beam carrying orbital angular momentum, thereby providing a terahertz polarization-maintaining vortex controller.

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0006] A twin rectangular graphene structure terahertz polarization-maintaining vortex controller, which is composed of unit structures periodically arranged on a plane, each unit structure is composed of a twin rectangular graphene layer, a silicon dioxide dielectric layer, and a metal matrix layer stacked in sequence from top to bottom, and the twin rectangular graphene layer is composed of two congruent rectangular graphene sheets arranged side by side with intervals.

[0007] Preferably, in the twin rectangular graphene layer, a single rectangular graphene sheet has a length of 5 μm to 8 μm, a width of 2 μm to 4 μm, and a thickness of 1 nm to 10 nm.

[0008] Preferably, in the twin rectangular graphene layer, the distance between two rectangular graphene sheets is 5 μm to 10 μm.

[0009] Preferably, the period of the unit structure is 10 μm to 50 μm.

[0010] Preferably, the thickness of the silicon dioxide dielectric layer is 10 μm to 100 μm.

[0011] Preferably, the metal base layer is made of copper.

[0012] Preferably, the thickness of the metal base layer is 0.1 μm to 1.0 μm.

[0013] Preferably, the terahertz polarization-maintaining vortex controller is formed by periodically and continuously arranging n×n different phase unit structures as encoding units on a plane, wherein each unit structure generates a different phase by changing the graphene Fermi level of the twin rectangular graphene layer.

[0014] Preferably, the graphene Fermi level varies in the range of 0 eV to 0.9 eV.

[0015] Preferably, all unit structures produce different phases by changing the graphene Fermi level, and the twin rectangular graphene layers produce different coding units at three frequency points of 3.2THz, 3.9THz and 4.2THz respectively. The coding units with different phases are arranged in different ways to realize vortex beams with different topological charges and different angle splitting, and the polarization state of the vortex beam remains consistent with the polarization state of the incident terahertz wave.

[0016] The twin rectangular graphene structure terahertz polarization-maintaining vortex controller designed by the present invention generates different phases by changing the graphene Fermi level. The twin rectangular graphene structure generates different coding units at three frequency points of 3.2THz, 3.9THz and 4.2THz respectively. The coding units with different phases are arranged in different ways to realize vortex beams with different topological charges and different angles, and the polarization state of the vortex beam is kept consistent with the polarization state of the incident terahertz wave. The present invention can solve the problem that the existing terahertz vortex cannot realize polarization-maintaining control. The design uses a twin rectangular graphene supersurface structure, combines the twin rectangular graphene supersurface arrangement and adjusts the graphene Fermi level, realizes the regulation of the terahertz vortex beam carrying orbital angular momentum, and has a very broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a three-dimensional schematic diagram of a twin rectangular graphene structure terahertz polarization-maintaining vortex controller unit;

[0018] Figure 2 It is the phase of the unit structure of the twin rectangular graphene structure terahertz polarization-maintaining vortex controller at different frequencies and different Fermi levels;

[0019] Figure 3 It is the amplitude and phase of the twin rectangular graphene structure THz polarization-maintaining vortex controller unit structure at frequencies of 3.2THz, 3.9THz and 4.2THz;

[0020] Figure 4 is the phase arrangement of the polarization-maintaining vortex controller of the twin rectangular graphene structure when the topological charge number l = ±1;

[0021] Figure 5 When the topological charge is l = ±1, the three-dimensional far-field and two-dimensional electric field diagrams of the twin rectangular graphene structure terahertz polarization-maintaining vortex controller, (a) f = 3.2 THz, (b) f = 3.9 THz, (c) f = 4.2 THz;

[0022] Figure 6 is the phase arrangement of the polarization-maintaining vortex controller of twin rectangular graphene structure when the topological charge number l = ±2;

[0023] Figure 7 When the topological charge is l = ±2, the three-dimensional far-field and two-dimensional electric field diagrams of the twin rectangular graphene structure terahertz polarization-maintaining vortex controller, (a) f = 3.2 THz, (b) f = 3.9 THz, (c) f = 4.2 THz;

[0024] Figure 8 Phase arrangement of the twin rectangular graphene structure terahertz polarization-maintaining vortex controller when the topological charge number l = ±3;

[0025] Fig. 9 When the topological charge is l = ±3, the three-dimensional far-field and two-dimensional electric field diagrams of the twin rectangular graphene structure terahertz polarization-maintaining vortex controller, (a) f = 3.2 THz, (b) f = 3.9 THz, (c) f = 4.2 THz. DETAILED DESCRIPTION

[0026] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation mode of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0027] In a preferred embodiment of the present invention, a twin rectangular graphene structure terahertz polarization-maintaining vortex controller is provided. It is composed of a series of identical unit structures periodically arranged on a plane, and each unit structure is composed of a twin rectangular graphene layer 1, a silicon dioxide dielectric layer 2, and a metal matrix layer 3 stacked in sequence from top to bottom. Among them, the twin rectangular graphene layer 1 is composed of two congruent rectangular graphene sheets arranged side by side, the long sides of the two rectangular graphene sheets are parallel and a certain interval is maintained between the two rectangular graphene sheets. The outer contour of the plane of each unit structure in the overall top-down perspective is a square.

[0028] When the above-mentioned terahertz polarization-maintaining vortex controller is arranged periodically, it can be arranged in an n×n array form, where n is a positive integer. These n×n unit structures can be used as coding units to form a metasurface, and these unit structures can produce different phases by changing the graphene Fermi level of the twin rectangular graphene layer 1. In an embodiment of the present invention, the variation range of the above-mentioned graphene Fermi level is 0eV~0.9eV, which can form a continuous reflection phase change. In the entire terahertz polarization-maintaining vortex controller, all unit structures produce different phases by changing the graphene Fermi level, and the twin rectangular graphene layer 1 produces different coding units at three frequency points of 3.2THz, 3.9THz and 4.2THz respectively. The coding units with different phases are arranged in different ways to realize vortex beams with different topological charges and different angles, and the polarization state of the vortex beam remains consistent with the polarization state of the incident terahertz wave.

[0029] The specific materials and parameters of the twin rectangular graphene structure terahertz polarization-maintaining vortex controller are as follows:

[0030] In the twin rectangular graphene layer 1, the length of a single rectangular graphene is 5 μm to 8 μm, the width is 2 μm to 4 μm, and the thickness is 1 nm to 10 nm. In the twin rectangular graphene layer 1, the spacing between two rectangular graphene sheets is 5 μm to 10 μm. The side length of the square outer contour of the unit structure is defined as the period side length, and the period of the unit structure is 10 μm to 50 μm. The thickness of the silicon dioxide dielectric layer 2 is 10 μm to 100 μm. The material of the metal substrate layer 3 is metal copper. The thickness of the metal substrate layer 3 is 0.1 μm to 1.0 μm.

[0031] The graphene used in the present invention has the characteristics of high electrical tunability and low surface loss, and is suitable for designing terahertz devices. The graphene metasurface uses its own unique electrical properties to adjust the graphene Fermi level to obtain different reflection phases, thereby achieving control of the vortex beam.

[0032] The above-mentioned twin rectangular graphene structure terahertz polarization-maintaining vortex controller is applied to a specific example below to demonstrate its technical effect.

[0033] Example

[0034] In this embodiment, the shapes of the components of the designed twin rectangular graphene structure terahertz polarization-maintaining vortex controller are as described above. Figure 1 , which will not be described here. The specific parameters of a single unit structure in the twin rectangular graphene structure terahertz polarization-maintaining vortex controller are as follows:

[0035] In the twin rectangular graphene layer 1, the length of a single rectangular graphene is 6 μm, the width is 3 μm, and the thickness is 10 nm. In the twin rectangular graphene layer 1, the spacing between two rectangular graphene sheets is 8 μm. The period of the unit structure is 10 μm. The thickness of the silicon dioxide dielectric layer 2 is 10 μm. The material of the metal substrate layer 3 is copper metal, and the thickness is 0.5 μm.

[0036] The unit structure uses the unique electrical properties of graphene to adjust the size of the graphene Fermi level to obtain different reflection phases. Figure 2 It is the phase of the twin rectangular graphene structure terahertz polarization-maintaining vortex controller unit structure at different frequencies and different Fermi levels. It can be seen from the figure that within the 2-5THz frequency band, the Fermi level of graphene is regulated in the range of 0-1eV to achieve continuous phase change, and the phase covers 0-2π.

[0037] According to the amplitude and phase requirements for achieving OAM, three frequencies of 3.2 THz, 3.9 THz and 4.2 THz are selected, and eight unit structures with different Fermi levels are selected for encoding. The phase difference between adjacent coding units is about π / 4. The specific naming of the coding units is shown in Tables 1, 2 and 3.

[0038] Table 1 Fermi levels and phases of eight coding units at 3.2 THz

[0039]

[0040] Table 2 Fermi levels and phases of eight coding units at 3.9 THz

[0041]

[0042] Table 3 Fermi levels and phases of eight coding units at 4.2 THz

[0043]

[0044] Figure 3 The amplitude and phase curves of the coding unit at frequencies of 3.2THz, 3.9THz, and 4.2THz are given. Figure 3 (a) represents the amplitude and phase curves of the coding unit at a frequency of 3.2 THz. The eight structural units are coded as A1-A8, and the corresponding graphene Fermi levels are 0, 0.2, 0.27, 0.39, 0.45, 0.56, 0.75, 0.85 eV and the corresponding phases are 32, 76, 123, 168, 211, 258, 302, 349°; Figure 3 (b) represents the amplitude and phase curves of the coding unit at a frequency of 3.9 THz. The eight structural units are coded as B1-B8, and the corresponding graphene Fermi levels are 0.4, 0.47, 0.51, 0.79, 0.9, 0.11, 0.25, and 0.3 eV and the corresponding phases are 13, 61, 105, 153, 195, 242, 290, and 339°; Figure 3 (c) shows the amplitude and phase curves of the coding unit at a frequency of 4.2 THz. The eight structural units are coded C1-C8, and the corresponding graphene Fermi levels are 0.5, 0.63, 0.81, 0, 0.13, 0.28, 0.34, and 0.4 eV and the corresponding phases are 10, 58, 102, 150, 194, 240, 286, and 332°. The reflection amplitudes of the eight basic units are all greater than 0.7, and the phases are evenly distributed in the range of 0-2π, which meets the coding requirements.

[0045] Figure 4 The metasurface phase distribution diagram of the vortex beam with topological charge number l = ±1 is given. The encoding unit is arranged and simulated according to the phase distribution diagram using CSTMicrowave Studio commercial software. The results are as follows: Figure 5 As shown, Figure 5The three-dimensional far field and two-dimensional electric field diagrams of the twin rectangular graphene structure THz polarization-maintaining vortex controller when the topological charge is l = ±1, where (a) is f = 3.2THz, (b) is f = 3.9THz, and (c) is f = 4.2THz. By changing the graphene Fermi level of the metasurface unit, the topological charge of the vortex beam can be dynamically adjusted between l = +1 (l = -1), l = +2 (l = -2), and l = +3 (l = -3) while keeping the polarization state unchanged.

[0046] Figure 6 The metasurface phase distribution diagram of the vortex beam with a topological charge of l = ±2 is shown in Figure 1. The encoding units are arranged and simulated according to the phase distribution diagram using CST MicrowaveStudio commercial software. The results are shown in Figure 1. Figure 7 As shown, Figure 7 The three-dimensional far-field and two-dimensional electric field diagrams of the twin rectangular graphene structure terahertz polarization-maintaining vortex controller when the topological charge is l=±2, where (a) is f=3.2THz, (b) is f=3.9THz, and (c) is f=4.2THz.

[0047] Figure 8 The metasurface phase distribution diagram of the vortex beam with a topological charge of l = ±3 is shown in Figure 1. The encoding units are arranged and simulated according to the phase distribution diagram using CST MicrowaveStudio commercial software. The results are shown in Figure 1. Fig. 9 As shown, Fig. 9 The three-dimensional far-field and two-dimensional electric field diagrams of the twin rectangular graphene structure terahertz polarization-maintaining vortex controller when the topological charge is l=±3, where (a) is f=3.2THz, (b) is f=3.9THz, and (c) is f=4.2THz.

[0048] In this embodiment, a twin rectangular graphene structure terahertz polarization-maintaining vortex controller is designed to produce different phases by changing the graphene Fermi level. The twin rectangular graphene structure produces different coding units at three frequency points of 3.2THz, 3.9THz and 4.2THz, respectively. The coding units with different phases are arranged in different ways to realize vortex beams with different topological charges and different angle splitting, and the polarization state of the vortex beam remains consistent with the polarization state of the incident terahertz wave.

[0049] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A twin rectangular graphene structure terahertz polarization-maintaining vortex controller, characterized in that: It is composed of unit structures periodically arranged on a plane, each unit structure is composed of a twin rectangular graphene layer (1), a silicon dioxide dielectric layer (2), and a metal matrix layer (3) stacked in sequence from top to bottom, and the twin rectangular graphene layer (1) is composed of two congruent rectangular graphene sheets arranged side by side with an interval.

2. The twin rectangular graphene structure terahertz polarization-maintaining vortex controller according to claim 1, characterized in that: In the twin rectangular graphene layer (1), a single rectangular graphene sheet has a length of 5 μm to 8 μm, a width of 2 μm to 4 μm, and a thickness of 1 nm to 10 nm.

3. The twin rectangular graphene structure terahertz polarization-maintaining vortex controller according to claim 1, characterized in that: In the twin rectangular graphene layer (1), the distance between two rectangular graphene sheets is 5 μm to 10 μm.

4. The twin rectangular graphene structure terahertz polarization-maintaining vortex controller according to claim 1, characterized in that: The period of the unit structure is 10 μm to 50 μm.

5. The twin rectangular graphene structure terahertz polarization-maintaining vortex controller according to claim 1, characterized in that: The thickness of the silicon dioxide dielectric layer (2) is 10 μm to 100 μm.

6. The twin rectangular graphene structure terahertz polarization-maintaining vortex controller according to claim 1, characterized in that: The material of the metal base layer (3) is metal copper.

7. The twin rectangular graphene structure terahertz polarization-maintaining vortex controller according to claim 1, characterized in that: The thickness of the metal matrix layer (3) is 0.1 μm to 1.0 μm.

8. The twin rectangular graphene structure terahertz polarization-maintaining vortex controller according to claim 1, characterized in that: The terahertz polarization-maintaining vortex controller is formed by periodically and continuously arranging n×n different phase unit structures as encoding units on a plane, wherein each unit structure generates a different phase by changing the graphene Fermi level of the twin rectangular graphene layer (1).

9. The twin rectangular graphene structure terahertz polarization-maintaining vortex controller according to claim 8, characterized in that: The graphene Fermi level varies in the range of 0 eV to 0.9 eV.

10. The twin rectangular graphene structure terahertz polarization-maintaining vortex controller according to claim 8, characterized in that: All unit structures generate different phases by changing the graphene Fermi level. The twin rectangular graphene layers (1) generate different coding units at three frequency points of 3.2 THz, 3.9 THz and 4.2 THz respectively. The coding units with different phases are arranged in different ways to realize vortex beams with different topological charges and different angles. The polarization state of the vortex beam remains consistent with the polarization state of the incident terahertz wave.

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