A plane wave to spherical wave phased array chip based on graphene metasurface

Abstract

This invention provides a plane-to-spherical wave phased array chip based on graphene metasurfaces, comprising a reflective metasurface phased array; the reflective metasurface phased array includes M×M periodically arranged graphene metasurface units; each graphene metasurface unit includes a graphene patch with a circular upper surface and a dielectric substrate below; the geometric centers of the circular graphene patch and the dielectric substrate are aligned. This invention utilizes the characteristic of graphene metasurface units to achieve 0–360° full-phase modulation of the electric field of the incident wave, realizing the conversion of plane waves into spherical waves within a frequency range of 50 THz to 60 THz, and possessing the advantages of wide bandwidth, planarization, and single-layer structure.

Description

Technical Field

[0001] The present invention relates to the field of wireless communications, and in particular to a plane wave to spherical wave phased array chip based on a graphene metasurface. Background Art

[0002] In recent years, with the rapid development of wireless communication technology, people have higher and higher requirements on the performance and size of devices. Electromagnetic metasurface is a two-dimensional planar array composed of periodic or non-periodic subwavelength unit structures, which has extraordinary physical properties that natural materials do not have. Electromagnetic metasurface is a two-dimensional electromagnetic material with relatively thin and light weight, small size and simple structure. It can flexibly control the amplitude, phase and polarization state of electromagnetic waves (Xiangang, L. Priciples of Electromagnetic Waves in Metasurface [J]. Science China, 2015, 58 (9): 594-201), and is widely used in irregular reflection or refraction, reflective array antennas and polarization converters.

[0003] Graphene is a new type of super surface composed of a single layer of carbon atoms, with unique optical properties. Compared with materials such as precious metals, graphene has lower transmission loss and stronger electromagnetic control capabilities (Grigorenko, AN; Polini, M.; Novoselov, KS Graphene Plasmonics [J]. Nature Photonic, 2012, 6 (11): 749-758.). At the same time, the chemical potential of graphene can be regulated by chemical doping and external electrostatic voltage, thereby changing the surface conductivity of graphene, and flexibly regulating the beam shape, transmission path and polarization direction of electromagnetic waves to achieve the adjustment of device performance (Sudipta, RB; Cristian, EG; Andrei, N.; In-Ho, L.; Sang-Hyun, O.; Phaedon, A.; Tony, L. Tunable Graphene Metasurface Reflectarray for Cloaking, Illusion, and Focusing [J]. Physical Review Applied, 2018, 9 (3): 034021). Traditional waveform conversion arrays mostly use metal units as unit structures, which often require more complex feeding networks, making the cost higher, the structure size more complex, and also have greater material loss. By designing the geometric characteristics such as the shape of the graphene metasurface, plane electromagnetic waves can be converted into spherical waves in the mid-infrared band, and the structure is simple, the working frequency band is wide, and it is more conducive to integration. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and to propose a plane wave to spherical wave phased array chip based on a graphene metasurface, which is used to solve the technical problems of excessive loss and narrow bandwidth in the prior art.

[0005] The present invention adopts the following technical solution:

[0006] A plane wave to spherical wave phased array chip based on a graphene metasurface, comprising a reflective metasurface phased array; the reflective metasurface phased array comprises M×M periodically arranged graphene metasurface units, M≥20; the graphene metasurface unit comprises a graphene patch with a circular structure on the upper surface and a dielectric substrate below.

[0007] Preferably, the graphene patch is a circular structure, and its radius R ranges between 0.05 microns and 0.5 microns.

[0008] Preferably, the lower dielectric substrate is made of Rogers RO4003 material, and the cross-section of the lower dielectric substrate is a square with a side length p of 1 micron and a thickness h of 0.6 micron.

[0009] Preferably, there is no gap between the graphene patch and the underlying dielectric substrate.

[0010] Preferably, the geometric center of the graphene patch and the underlying dielectric substrate are in a straight line.

[0011] Preferably, the reflective metasurface phased array can convert plane waves into spherical waves in the frequency range of 50 THz to 60 THz.

[0012] Preferably, the compensation phase required by the graphene metasurface unit at each position when the plane wave is converted to the spherical wave is as follows:

[0013]

[0014] Wherein, x and y represent the abscissa and ordinate of the graphene supersurface unit respectively; M represents the number of periodic units; λ0 represents the wavelength corresponding to the operating frequency, and p represents the period length of the supersurface unit.

[0015] Preferably, the cross-section of the periodically arranged graphene supersurface units forms a rectangular, circular or other polygonal structure.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The reflective metasurface phased array of the present invention can operate in the mid-infrared frequency band, and the bandwidth can cover the frequency range of 50THz to 60THz;

[0018] (2) The reflective metasurface phased array of the present invention can achieve perfect conversion of spatial plane electromagnetic waves into spherical waves, and the array structure has the advantages of planarization, easy processing, and integration;

[0019] (3) The reflective metasurface phased array of the present invention has a large phase modulation range and can achieve a phase change of 0° to 360° within the frequency range of 50THz to 60THz.

[0020] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention so that it can be implemented in accordance with the contents of the specification, and in order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below.

[0021] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of the three-dimensional structure of the plane wave to spherical wave phased array chip based on the graphene metasurface of this embodiment;

[0023] Figure 2 is a schematic diagram of the three-dimensional structure of the graphene supersurface unit of this embodiment;

[0024] Figure 3 is a reflection phase distribution diagram of the graphene metasurface unit of this embodiment;

[0025] Figure 4 It is the reflected electric field phase diagram of the reflective metasurface phased array of this embodiment at 50THz to 60THz. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0027] See also Figure 1As shown, it is a schematic diagram of the three-dimensional structure of the plane wave to spherical wave phased array chip based on the graphene metasurface of this embodiment. The plane wave to spherical wave phased array chip based on the graphene metasurface includes M×M graphene metasurface units 1. In this specific embodiment, M=50. Each graphene metasurface unit 1 is arranged seamlessly with each other to form a reflective metasurface phased array 2 with a rectangular structure. The surface size of the reflective metasurface phased array 2 is 50 microns×50 microns.

[0028] See also Figure 2 As shown, it is a schematic diagram of the three-dimensional structure of a single graphene super surface unit 1, which includes a graphene patch 11 with a circular upper surface shape and a dielectric substrate 12 with a square cross section below. In this embodiment, the radius R of the graphene circular patch 11 varies between 0.05 microns and 0.5 microns (in M×M graphene super surface units 1, the radius of the corresponding graphene circular patch may be different, but the size of the dielectric substrate 12 is the same). The dielectric substrate 12 uses Rogers RO4003 material with a dielectric constant of 3.55, and the cross section of the dielectric substrate 12 is a square, with a side length p of 1 micron and a thickness h of 0.6 microns. In this embodiment, there is no gap between the graphene patch 11 and the dielectric substrate 12, and the geometric centers of the graphene patch 11 and the dielectric substrate 12 are on a straight line.

[0029] The present invention proposes a plane wave to spherical wave phased array chip based on a graphene metasurface, which is composed of 50×50 graphene metasurface units 1. Wherein, x and y are the horizontal and vertical coordinates of the graphene metasurface unit 1, M=50 is the number of metasurface units, λ0 is the wavelength corresponding to the working frequency, and p=1 micron is the period length of the metasurface unit. The compensation phase required by the graphene metasurface unit 1 at each position when the plane wave is converted to the spherical wave is determined, and the reflective metasurface phased array 2 is constructed according to this distribution law. When a plane electromagnetic wave is vertically incident on the reflective metasurface phased array, the electric field phase of the plane wave is regulated by the compensation phase of the graphene metasurface unit at each position, and a spherically distributed electromagnetic wave can be obtained by reflection in the upper near field area of ​​the reflective metasurface phased array, realizing the function of converting the plane wave into a spherical wave in the mid-infrared frequency domain.

[0030] The following is a further explanation of the technical effects of the present invention in combination with simulation experiments.

[0031] 1. Simulation conditions and contents:

[0032] The simulation frequency range is set to 50 THz to 60 THz, the relaxation time of graphene is 1 ps, and the commercial simulation software HFSS_19.0 is used to perform the above specific embodiment:

[0033] Simulation 1: When the operating frequency is 50THz, 54THz, and 60THz, the reflection phase response of the graphene metasurface unit in this embodiment is simulated by changing the radius of the graphene patch and the chemical potential of the graphene patch, see Figure 3 As shown;

[0034] Simulation 2, setting the incident wave as a plane electromagnetic wave, simulates the electric field phase of the reflected wave from the plane wave to the spherical wave phased array chip based on the graphene metasurface in this embodiment at operating frequencies of 50THz, 52THz, 54THz, 56THz, 58THz, and 60THz, respectively. Figure 4 shown.

[0035] 2. Analysis of simulation measurement results:

[0036] See also Figure 3 As shown, it shows the relationship between the reflection phase of the graphene metasurface unit and the graphene patch radius and the graphene chemical potential when the operating frequencies are 50THz, 54THz, and 60THz respectively. At 50THz, when the radius of the graphene patch increases from 0.05 microns to 0.5 microns, the chemical potential of graphene is set to 0.831eV and 0.106eV respectively, which can make the reflection phase change from 0° to 360°; at 54THz, the chemical potential of graphene is set to 0.83eV and 0.114eV respectively, which can also make the reflection phase change from 0° to 360°; at 60THz, the chemical potential of graphene is set to 0.832eV and 0.125eV respectively, which also makes the reflection phase change from 0° to 360°. Verification by simulation results has confirmed that within the frequency range of 50THz to 60THz, the reflection phase of the graphene metasurface can change from 0° to 360°, which is consistent with the theory of the plane wave to spherical wave phased array chip based on the graphene metasurface proposed in the present invention.

[0037] See also Figure 4 As shown in the figure, the reflected electric field phase distribution diagram of the reflective metasurface phased array at working frequencies of 50THz, 52THz, 54THz, 56THz, 58THz, and 60THz is shown. The sampling plane is set above the phased array at 24 microns from the working plane. The reflected electric field phase distribution diagram shows good spherical wave characteristics. The simulation results show that in the wide frequency range of 50THz to 60THz, the metasurface phased array can convert the incident plane electromagnetic wave into a reflected spherical wave, meeting the bandwidth requirements of modern communications.

[0038] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A plane wave to spherical wave phased array chip based on graphene metasurface, characterized by: It comprises a reflective metasurface phased array; the reflective metasurface phased array comprises M×M periodically arranged graphene metasurface units, M≥20; the graphene metasurface unit comprises a graphene patch with a circular structure on the upper surface and a dielectric substrate below; The reflective metasurface phased array can convert plane waves into spherical waves in the frequency range of 50THz to 60THz; The compensation phase required by the graphene metasurface unit at each position when the plane wave is converted to the spherical wave is as follows: Wherein, x and y represent the abscissa and ordinate of the graphene supersurface unit respectively; M represents the number of periodic units; λ0 represents the wavelength corresponding to the operating frequency, and p represents the period length of the supersurface unit.

2. The plane wave to spherical wave phased array chip based on graphene metasurface according to claim 1, characterized in that: The graphene patch is a circular structure, and its radius R ranges between 0.05 micrometers and 0.5 micrometers.

3. The plane wave to spherical wave phased array chip based on graphene metasurface according to claim 1, characterized in that: The lower dielectric substrate is made of Rogers RO4003 material, and the cross-section of the lower dielectric substrate is a square, with a side length p of 1 micron and a thickness h of 0.6 micron.

4. The plane wave to spherical wave phased array chip based on graphene metasurface according to claim 1, characterized in that: There is no gap between the graphene patch and the underlying dielectric substrate.

5. The plane wave to spherical wave phased array chip based on graphene metasurface according to claim 1, characterized in that: The geometric center of the graphene patch and the underlying dielectric substrate are in a straight line.

6. The plane wave to spherical wave phased array chip based on graphene metasurface according to claim 1, characterized in that: The cross-section of the periodically arranged graphene supersurface units forms a rectangular, circular or other polygonal structure.

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