An active tunable terahertz functional metamaterial based on hybrid-graphene vanadium dioxide

In this paper, we propose a switchable and tunable functional metamaterial device based on hybrid graphene-vanadium dioxide (VO2). Using the properties of the metal-insulator transition in VO2, the proposed metamaterials can enable switching between tunable circular dichroism (CD) and dual-band perfect absorption in the terahertz region. When VO2 is in the insulator state, a polarization-selective single-band perfect absorption can be achieved for circularly polarized waves, thus resulting in a strong CD response with a maximum value of 0.84. When VO2 acts as a metal, there is a tunable dual-band perfect absorption for the designed metamaterial device under the illumination of x-polarization waves. The operation mechanism behind the phenomena can be explained by utilizing the electric field distribution and the coupled mode theory. Moreover, the influences of the Fermi energy of graphene and geometrical parameters on the CD and absorption spectra are discussed in detail. Our proposed switchable and tunable metamaterial can provide a platform for designing versatile functional devices in the terahertz region.