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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 (${{\rm VO}_2}$) and graphene is proposed. Due to the phase transition of ${{\rm VO}_2}$ and the electrically tunable properties of graphene, the structure realizes single broadband and dual-band absorption characteristics. When graphene is in the insulating state (${E_f} = {0}\;{\rm eV}$) and ${{\rm VO}_2}$ 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 ${{\rm VO}_2}$ 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 (${E_f} = {1}\;{\rm eV}$), ${{\rm VO}_2}$ 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.
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