Thermally switchable bifunctional plasmonic metasurface for perfect absorption and polarization conversion based on VO2

Perfect absorption and polarization conversion of electromagnetic wave (EM) are of significant importance for numerous optical applications. Vanadium dioxide (VO2), which can be converted from insulating state to metallic state by being exposed to different temperatures, is introduced into a metallic square loop to constitute a switchable bifunctional plasmonic metasurface for perfect absorption and polarization conversion. Combined theoretical analyses and numerical simulations, the results show that at temperature T = 356 K, the metasurface acts as a perfect absorber with nearly 91% absorptance at the wavelength of 1547 nm. When the temperature decreases to T = 292 K, the metasurface expresses as a high efficiency (about 94%) polarization converter with the polarization conversion ratio up to 86% around 1550 nm. The designed bifunctional metasurface has plenty of potential applications such as energy harvesting, optical sensing and imaging. Moreover, it can also provide guidance to research tunable, smart and multifunctional devices.