Reconfigurable broadband metasurfaces with nearly perfect absorption and high efficiency polarization conversion in THz range

Reconfigurable metasurfaces (RMSs) that enable the switching function of absorption and polarization conversion have attracted increasing attention. However, the design of RMSs to achieve wideband and high efficiency for both absorption and polarization conversion functions simultaneously remains a great challenge. Here, we propose the design of a RMS structure with a high-efficiency cross-polarization conversion and nearly perfect absorption. The reconfiguration between different functions of polarization conversion and absorption is obtained based on the reversible insulator-to-metal phase transition of Vanadium dioxide (VO2). When the VO2 is in insulator state, the RMS realizes the cross-polarization conversion function in the wideband of 1.04-3.75 THz with a relative bandwidth up to 113 % due to the multi-resonant modes of electric and magnetic resonances. Meanwhile, the nearly-perfect absorption is achieved in the range of 1.36-3.38 THz with the corresponding relative bandwidth up to 85 %for the VO2 in metallic state. Specially, the wideband and high-efficiency performance of these functionalities is maintained for a wide angle incidence. The capability of bi-functional switch and integration with polarization conversion and absorption in a single metasurface structure endowed with both wideband and high-efficiency characteristics for a wide incident angle is very promising for emerging RMS devices in the terahertz region.