Dynamically tunable multifunctional terahertz absorber based on hybrid vanadium dioxide and graphene metamaterials

Abstract

In this work, in pursuit of a multifunctional device with a simple structure, high absorption rate, and excellent bandwidth, a tunable broadband terahertz (THz) absorber based on vanadium dioxide (VO2) and graphene is proposed. Due to the phase transition of VO2 and the electrically tunable properties of graphene, the structure realizes single broadband and dual-band absorption characteristics. When graphene is in the insulating state (E f =0eV) and VO2 is in the metallic state, the developed system has more than 90% absorption and a wide absorption band from 1.36 to 5.48 THz. By adjusting the VO2 conductivity, the bandwidth absorption can be dynamically varied from 23% to more than 90%, which makes it a perfect broadband absorber. When graphene is in the metallic state (E f =1eV), VO2 is in the insulating state, and the designed device behaves as a tunable and perfect dual-band absorber, where the absorptivity of the dual-band spectrum can be continuously adjusted by varying the Fermi energy level of graphene. In addition, both the broad absorption spectrum and the dual-band absorption spectrum maintain strong polarization-independent properties and operate well over a wide incidence angle, and the designed system may provide new avenues for the development of terahertz and other frequency-domain tunable devices.