Composite phase modulated beam steering controllable reflective metasurface

Abstract

Terahertz metasurface functional devices have attracted extensive attention from researchers as an effective method to control terahertz waves. In order to enhance the functionality and flexibility of the metasurface and adapt to diverse application scenarios and demands, this paper designs a beam-steering controllable reflective metasurface by combining the Pancharatnam-Berry phase principle and the phase change material vanadium dioxide. The metasurface unit consists of five layers, the top layer is a metal patterned layer, the third layer of vanadium dioxide is located between different thicknesses of the dielectric layer, the material of the dielectric layer is PTFE, and the bottom layer is a metal reflective layer. The metasurface unit are rotated based on the Pancharatnam-Berry phase principle to obtain four metasurface units with fixed phase differences, after which the metasurface units are arranged in two dimensions based on the generalized Snell reflection law to obtain the desired phase-gradient deflected reflection beam. The insulating state-metallic state transition of the vanadium dioxide layer on the metasurface can change the phase gradient of the preset metasurface, thus realizing the on-off of the deflection function. The simulation results show that: when the vanadium dioxide is in the insulating state, the phase gradient of the designed metasurface, the metasurface can deflect the vertically incident circularly polarized wave with specific angle anomalies within the operating band of 1.1~2.0 THz; when the vanadium dioxide is in the metallic state, for the same operating band of the same metasurface, the phase gradient of the metasurface disappears, and the metasurface mirror reflection vertically incident circularly polarized waves, realizing of function switching. This design provides new possibilities in the field of terahertz reflected beam modulation, which will have potential applications in terahertz wireless communication and radar systems.