VO2-Graphene based four-state ultra-wideband terahertz metamaterial with switchable absorption, reflection, and transmission

A multifunctional ultra-wideband (UWB) terahertz (THz) metamaterial device based on VO2 and graphene is proposed, capable of achieving tunable and switchable high-frequency absorption broadband (HFBA)/low-frequency broadband absorption (LFBA)/reflection/transmission in the THz band. The mechanism is clearly explained by impedance matching theory, the electric field strength distributions (EFSDs) and equivalent simplified model. Based on the simulation results, the localized surface plasmon resonance (LSPR) of the patterned graphene reaches LFBA above 90 % between 2.42 and 4.83 THz, and the absorptivity can be changed from 19 % to 99 % by varying the graphene's Fermi level. The electric and magnetic resonances produce HFBA with an adjustable absorption amplitude between 17 % and 98 % in the 3.02-7.86 THz range by controlling the conductivity of the annular VO2. In addition, reflection and transmission can be adjusted between 0 % and 80 %. The proposed metamaterial device exhibits strong polarization- and angle-of-incidence-independent properties, ensuring its stable application in intelligent absorption and electromagnetic shielding.