Abstract
Coding metasurfaces incorporated with reconfigurable elements can dynamically control electromagnetic waves to realize reconfigurable multiple functionalities. The mostly existing active devices usually work in microwave band and have little ability to dynamically control terahertz waves. Here, a graphene-based coding metasurface (GBCM) is presented to realize dynamic beam steering for terahertz waves. The coding state “1” of the proposed GBCM can be continuously tuned to “0” by Fermi level of an integral graphene film. In order to verify the working principle, two examples are designed to demonstrate the dynamic tunability of the proposed GBCM for terahertz waves. One is dynamic multi-beam switching and another is dynamic diffusion switching. Under the normal illumination of terahertz waves, a 1D periodic-sequence GBCM produces dual-, tri- and single-beam by setting Fermi level as 0.05 eV, 0.15 eV and 0.70 eV, respectively. Similarly, a 2D periodic-sequence GBCM produces quad-, penta- and single-beam by setting Fermi level as 0.05 eV, 0.11 eV and 0.70 eV, respectively. In the case of aperiodic coding sequence, reflected waves can be dynamically switched from diffusion to mirror reflection by increasing Fermi level from 0.05 eV to 0.70 eV. The above functionalities are well verified by theoretical calculations and numerical simulations.
Highlights
D IFFERENT from natural materials, metamaterial is a material consisting of artificial subwavelength structures, and it owns unusual electromagnetic (EM) behaviors
According to the proposed working principle and element design method, two kinds of beam steering are designed for terahertz wave
A general graphene-based coding metasurface (GBCM) is presented for terahertz wave
Summary
D IFFERENT from natural materials, metamaterial is a material consisting of artificial subwavelength structures, and it owns unusual electromagnetic (EM) behaviors. By introducing two types of unit cells with 0 and π phase responses to mimic “0” and “1” elements, they realized 1-bit description of the coding metasurface, and it can manipulate EM waves to realize multi-beam reflection and diffusion functions. With a gradient coding sequence, 2-bit coding metasurface can reflect a normally incident wave to a desired oblique angle They presented a biased diode-based digital metasurface, and it can be dynamically encoded by field-programmable gate array (FPGA) hardware to realize dynamic switching between multiple functions without changing the physical size of unit cells. A novel GBCM is presented, and its coding state can be continuously and dynamically manipulated by Fermi level of an integral graphene film. Using Matlab and finite-element-method (FEM), theoretical calculations agree well with simulations
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