Multi-Functional Wideband Metasurface: Perfect Absorber and Linear to Linear and Linear to Circular Polarization Converter

In this paper, a switchable multi-functional wideband metasurface device based on vanadium dioxide (VO2) in the terahertz (THz) region is numerically proposed. By controlling the phase of VO2, the functions of the proposed structure can be reversibly switched between a perfect absorber and two different polarization conversions. When VO2 is in the metallic phase, the absorption response can be achieved with an absorption rate above 0.9 in the range of 1.42 - 4.13 THz for wide-angle incidence, contributed by the highly lossy feature of VO2 metallic. Meanwhile, when VO2 acts as an insulator phase, the proposed metasurface exhibits linear-to-linear polarization conversion in the range of 1.27 - 3.53 THz and linear-to-circular polarization conversion in the frequency ranges of 1.08 - 1.24 THz and 3.65 - 5.27 THz simultaneously. This work opens new avenues for realizing multi-functional wideband metasurface devices in the terahertz range.