Terahertz absorber with switchable functionality from ultra-broadband to broadband

In this paper, we present a terahertz absorber with switchable absorption modes by utilizing patterned graphene-vanadium dioxide. Through thermal tuning of vanadium dioxide and electrical control of graphene, our device demonstrates two distinct absorption modes that can be switched between. By maintaining the Fermi energy of graphene at 1 eV, the device achieved an ultra-broadband absorption with a bandwidth of 4.62 THz, spanning from 3.58 to 8.20 THz, when the conductivity of vanadium dioxide reached 200,000 S/m. Once the conductivity dropped to 200 S/m, we observed a narrower bandwidth of 0.95 THz (ranging from 6.58 to 7.53 THz) for the broadband absorption. At this stage, manipulating the Fermi energy of graphene allows for control over the amplitude and frequency shift of the broadband mode. Additionally, the device benefits from a remarkable degree of symmetry, which guarantees its insensitivity to changes in polarization angle. The impact of geometric parameters on the robustness of absorption characteristics is also discussed. The device may have potential applications in broadband mirror and electromagnetic shielding and so on.