Switchable Terahertz Metasurfaces Based on Patterned Vanadium Dioxide and Graphene

Abstract

This paper proposes a bi-functional switchable broadband terahertz metasurface ground on U-shaped vanadium dioxide (VO2) and graphene. The proposed design can effectively switch the current working state through a two-parameter regulation mechanism. Specifically, as we fix graphene’s Fermi level at 1 eV, and VO2 is in the form of insulating, the proposed design can be seen as a broadband terahertz absorber. Shifting the Fermi level of graphene can dynamically modulate the amplitude of the broadband absorption spectrum. In other words, by arbitrarily tailoring the Fermi level of graphene, the proposed design can freely switch states, i.e., mode switching from broadband absorption to broadband reflection, in the frequency range of interest. As graphene’s Fermi level is equal to 0.01 eV, and the vanadium dioxide in the structure is in the metallic state; the designed metasurface can be seen as a broadband terahertz linear polarization converter. It can convert the incident linearly polarized terahertz wave into its orthogonal polarization. By varying the conductivity of vanadium dioxide in the simulation, the proposed design can freely tune the current operating state over the operating frequency range, similar to “ON” and “OFF”. Metasurfaces can work efficiently in different frequency ranges by changing the geometric parameters. Therefore, the designed structure has switchable and tunable functions simultaneously, providing additional options for integrated, intelligent, and miniaturized devices.