Terahertz Dynamic Beam Steering Based on Graphene Coding Metasurfaces

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.