Multifunctional active terahertz metasurface with electromagnetically induced transparency, perfect absorption, and circular dichroism

Navigated by the continued demand for design integration and miniaturization, incorporating multiple diversified operations into a single metasurface hybridized with the tunable metasurface is highly demanding at the terahertz (THz) range. However, up to now, because of the limitation of the reconfigurable metasurface at the terahertz range, most metasurfaces only feature a single function or process similar functionalities at a single frequency. A multi-functional terahertz metasurface based on vanadium dioxide (VO2) is proposed in this paper, which consists of a gold layer, a VO2 bridge, a SiO2 spacer, and a VO2 layer on the back of the spacer. Under different conductivity of different VO2 layers, the proposed metasurface achieves various terahertz device functions, including single-band perfect terahertz absorption, circular dichroism (CD) for the reflected and transmitted fields, and electromagnetically induced transparency (EIT) effect. Furthermore, the proposed metasurface exhibits robust response against oblique incidences. The mechanisms of perfect absorption, chiral-selective absorption and EIT are illustrated by impedance matching theory, surface current and electric field distributions, respectively. The function-switching ability of proposed metasurface provides more options for the design of terahertz devices in the future.