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Abstract
A multifunctional terahertz absorber based on a hybrid configuration of vanadium dioxide (${{\rm{VO}}_2})$ and graphene is proposed, which is enabled to dynamically switch between ultrabroadband and double-narrowband absorption characteristics using the phase-shifting property of ${{\rm{VO}}_2}$. When ${{\rm{VO}}_2}$ is in the metallic phase and the Fermi energy level of graphene is 0.01 eV, ultrabroadband absorption from 3.04 THz to 8.78 THz can be achieved. The absorption can be continuously adjusted from 0.7% to 99.9% by changing the conductivity of the ${{\rm{VO}}_2}$ through temperature. When ${{\rm{VO}}_2}$ is in the insulating phase and Fermi energy level of graphene is 0.4 eV, the proposed absorber exhibits a double-narrowband absorption characteristic, achieving 99.8% and 97.3% absorption at 1.79 THz and 4.62 THz, respectively. Since graphene is an electronically controlled material, it is able to dynamically modulate the resonant frequency and absorption intensity by changing the Fermi energy level of graphene. In addition, the physical mechanism of the multifunctional absorber is revealed using electric field distribution and the impedance-matching theory. The proposed absorber has potential applications in optical switching, image processing, and stealth technology.
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