Twinned rectangular graphene structure terahertz polarization maintaining vortex controller

Abstract

The application discloses a kind of twin rectangular graphene structure terahertz polarization maintaining vortex controllers, belong to the field of terahertz devices.The terahertz polarization maintaining vortex controller is composed of twin rectangular graphene layer, silicon dioxide dielectric layer, metal matrix layer, can change the conductivity of graphene by changing the Fermi energy level of graphene, produce the unit structure with different phase, arrange unit structure through different ways, realize different topological charge number and angle beam splitting terahertz vortex beam, and the polarization state of vortex beam keeps consistent with the polarization state of incident terahertz wave.The terahertz polarization maintaining vortex controller of the application has the advantages of simple structure, multiple functions, strong controllability, etc., and has very broad application prospect in the field of terahertz communication.

Description

Technical Field

[0001] The present 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 a circular amplitude field. The orbital angular momentum (OAM) they carry has an infinite number of eigenstates, each of which is determined by a topological charge number that can take on any integer value. The infinity of OAM modes and the orthogonality between these modes provide new degrees of freedom for electromagnetic wave modulation and information carrying. Within the terahertz (THz) frequency range, utilizing OAM technology enables the transmission of an infinite number of signals. Therefore, the manipulation of vortex waves in the THz region is expected to significantly increase the bandwidth and capacity of wireless communication systems, holding enormous potential for high-speed wireless communications. Vortex waves carrying OAM have attracted widespread attention from researchers both domestically and internationally. Current methods for generating vortex waves primarily include spiral phase plates, spiral reflectors, and circular array antennas. However, these methods, combined with their bulky device structures, complex systems, difficulty in fabrication, and high manufacturing costs, make them unsuitable for THz frequency ranges. Furthermore, once such devices are fabricated, the topological charge of their vortex waves is fixed and cannot be controlled, significantly limiting the potential applications of vortex wave beams. Therefore, developing small-scale, state-adjustable vortex wave generators is crucial for expanding the application 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. The structure generates vortex waves carrying orbital angular momentum in response to the incident terahertz wave. By utilizing the unique electrical properties of the graphene metasurface itself and adjusting the size of the graphene Fermi level, different reflection phases can be obtained, thereby achieving the adjustability of the vortex beam and allowing for flexible adjustment 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. The design uses a twin rectangular graphene metasurface structure, combines the twin rectangular graphene metasurface arrangement and adjusts the graphene Fermi level size to achieve the control of the terahertz vortex beam carrying orbital angular momentum, and provides a terahertz polarization-maintaining vortex controller.

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

[0006] A twin rectangular graphene structure terahertz polarization-maintaining vortex controller 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. 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, the length of a single rectangular graphene piece is 5 μm to 8 μm, the width is 2 μm to 4 μm, and the thickness is 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 angles, 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 produces different phases by changing the graphene Fermi level. The twin rectangular graphene structure generates different coding units at three frequencies: 3.2THz, 3.9THz, and 4.2THz. The coding units with different phases are arranged in different ways to realize vortex beams with different topological charges and different angles of beam splitting, and the polarization state of the vortex beam remains consistent with the polarization state of the incident terahertz wave. The present invention can solve the problem that existing terahertz vortexes cannot achieve polarization-maintaining control. The design and use of the twin rectangular graphene metasurface structure, combined with the twin rectangular graphene metasurface arrangement and the adjustment of the graphene Fermi level, can achieve the control of terahertz vortex beams carrying orbital angular momentum, and has very broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0019] Figure 3 The amplitude and phase of the twin rectangular graphene structure terahertz 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 twin rectangular graphene structure terahertz polarization-maintaining vortex controller when the topological charge number l = ±1;

[0021] Figure 5 3D far-field and 2D electric field diagrams of the terahertz polarization-maintaining vortex controller with a twin rectangular graphene structure when the topological charge is l = ±1, (a) f = 3.2 THz, (b) f = 3.9 THz, (c) f = 4.2 THz;

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

[0023] Figure 7 3D far-field and 2D electric field diagrams of the terahertz polarization-maintaining vortex controller with a twin rectangular graphene structure when the topological charge is l = ±2, (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] Figure 9 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 number is l = ±3, (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 objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention are described in detail below with reference to 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 than 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 the various embodiments of the present invention can be combined accordingly without conflicting with each other.

[0027] In a preferred embodiment of the present invention, a terahertz polarization-maintaining vortex controller with a twin rectangular graphene structure is provided. It is composed of a series of identical 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. The twin rectangular graphene layer 1 is composed of two congruent rectangular graphene sheets arranged side by side, with their long sides parallel and a certain distance between them. The outer contour of each unit structure, when viewed from above, 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 different phases can be generated between these unit structures 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 to 0.9eV, which can form a continuous reflection phase change. In the entire terahertz polarization-maintaining vortex controller, all unit structures generate different phases by changing the graphene Fermi level. The twin rectangular graphene layer 1 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 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 sheet 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 the two rectangular graphene sheets is 5 μm to 10 μm. The length of the square outer contour of the unit structure is defined as the period 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 base layer 3 is copper. The thickness of the metal base layer 3 is 0.1 μm to 1.0 μm.

[0031] The graphene used in this invention has high electrical tunability and low surface loss, making it suitable for designing terahertz devices. The graphene metasurface utilizes its unique electrical properties to adjust the graphene Fermi level to achieve 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 elaborated 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 twinned rectangular graphene layer 1, a single rectangular graphene sheet has a length of 6 μm, a width of 3 μm, and a thickness of 10 nm. The spacing between the two rectangular graphene sheets in the twinned rectangular graphene layer 1 is 8 μm. The unit structure period is 10 μm. The thickness of the silicon dioxide dielectric layer 2 is 10 μm. The metal substrate layer 3 is made of copper and has a thickness of 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 were selected, and eight unit structures with different Fermi levels were selected for encoding. The phase difference between adjacent coding units is approximately π / 4. The specific coding unit names are 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) 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, and 0.85 eV and the corresponding phases are 32, 76, 123, 168, 211, 258, 302, and 349°; Figure 3 (b) 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 as 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 a topological charge of l = ±1 is given. The encoding units are arranged and simulated according to the phase distribution diagram using CSTMicrowave Studio commercial software. The results are as follows: Figure 5 As shown, Figure 5Figures showing the 3D far-field and 2D electric field of a twin rectangular graphene structured terahertz polarization-maintaining vortex controller when the topological charge is l = ±1, where (a) is f = 3.2 THz, (b) is f = 3.9 THz, and (c) is f = 4.2 THz. By varying 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 maintaining the polarization state.

[0046] Figure 6 The metasurface phase distribution diagram of the vortex beam with a topological charge of l = ±2 is shown. The encoding units are arranged and simulated according to the phase distribution diagram using CST MicrowaveStudio commercial software. The results are as follows: 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 number is l = ±2, where (a) is f = 3.2 THz, (b) is f = 3.9 THz, and (c) is f = 4.2 THz.

[0047] Figure 8 The metasurface phase distribution diagram of the vortex beam with a topological charge of l = ±3 is shown. The encoding units are arranged and simulated according to the phase distribution diagram using CST MicrowaveStudio commercial software. The results are as follows: Figure 9 As shown, Figure 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 number is l = ±3, where (a) is f = 3.2 THz, (b) is f = 3.9 THz, and (c) is f = 4.2 THz.

[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 angles, and the polarization state of the vortex beam remains consistent with the polarization state of the incident terahertz wave.

[0049] The embodiment described above is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent substitution or equivalent transformation falls within the scope of protection 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 being 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, wherein the twin rectangular graphene layer (1) is composed of two congruent rectangular graphene sheets arranged side by side with an interval; The terahertz polarization-maintaining vortex controller is n×n Different phase unit structures are periodically and continuously arranged on a plane as coding units, wherein each unit structure generates a different phase by changing the graphene Fermi level of the twin rectangular graphene layer (1).

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), the length of a single rectangular graphene piece is 5 μm to 8 μm, the width is 2 μm to 4 μm, and the thickness is 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 the 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 base 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 graphene Fermi level varies in the range of 0 eV to 0.9 eV.

9. The twin rectangular graphene structure terahertz polarization-maintaining vortex controller according to claim 1, 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: 3.2THz, 3.9THz and 4.2THz. 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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