Transmission and reflection bi-direction terahertz encoding metasurface with a single structure

Most reported metasurfaces operate in single propagation direction mode (either transmissive mode or reflective mode), which hamper practical application. Here, we proposed a bi-directional operation coding metasurface based on a phase change material of a vanadium dioxide (VO₂) assisted metasurface. It can realize a dynamically invertible switch between the transmissive mode or reflective mode in the terahertz regime by changing the external ambient temperature. The proposed structure consists of a silicon column, polyimide dielectric substrate layer, and VO₂ film bottom layer. When VO₂ is in dielectric state, the designed metasurface possesses the functions of transmission beam splitting and deflection and generates a transmission vortex beam. When VO₂ is in metallic state, the proposed metasurface exhibits many functions such as reflection beam splitting, deflection, radar scattering surface (RCS) reduction and reflection vortex beam generation. The proposed metasurface can solve transmissive and reflective bi-direction terahertz encoding regulation. This scheme provides a new method to realize multi-function terahertz devices.