Tunable dual-functional metasurface for wideband cross-polarization conversion and wideband absorption

This work presents a tunable and wideband dual-functional metasurface (DFM) operating in the terahertz regime with highest overlap bandwidth (OBW). The structure consists of a double-split ring resonator and a meandered square ring resonator based on VO2 to achieve reflective cross-polarization conversion and absorption functionalities, respectively. When the phase changing material VO2 is in its metallic state, the metasurface acts as a perfect absorber with a peak absorption of >= 90% over the operating band of 2.3-4.01 THz. When VO2 is in its insulating state, the metasurface acts as a reflective cross-polarization converter over a wideband from 1-4.1 THz with high polarization conversion ratio of >= 90%. The proposed DFM has a stable response up to 45 degrees of incidence in the polarization converter state and 60 degrees of angular stability under the absorber state. Further, tunability is achieved by integrating photoconductive silicon and controlling the optical pump intensity in the double-split ring and meandered . square ring resonators. The proposed metasurface finds its applications in security, detection and THz communication systems.