Dynamic switching: vanadium dioxide and graphene-based terahertz perfect absorber for tunable broadband absorption and tri-band absorption

In this paper, a dual-function switchable perfect absorber in the terahertz band is simulated and proposed. The design leverages the phase transition properties of vanadium dioxide (VO2) and the dynamically tunable properties of graphene. The absorber exhibits broadband absorption when VO2 is operated in the insulating state alone, with a bandwidth of 7.09 THz and a high modulation depth of 99.45% resulting in absorption levels above 90%. Additionally, by operating the graphene square ring and the graphene round ring at the Fermi levels of 0.72 eV and 0.75 eV, respectively, the absorber demonstrates tri-band absorption, making it suitable for refractive index sensing applications. The absorber's operating frequency can be easily tuned by adjusting the conductivity of VO2 and the Fermi levels of graphene, enabling dynamic tunability. The feasibility of our work positions it as a promising candidate for designing switchable broadband and multi-band absorbers. Consequently, our research holds significant potential for applications in terahertz devices.