Dual-regulated broadband terahertz absorber based on vanadium dioxide and graphene

A tunable broadband terahertz (THz) absorber based on vanadium dioxide ( V O 2 ) and graphene is proposed. The absorber, consisting of the V O 2 square loop, polymethacrylimide (PMI) dielectric layer, and a layer of unpatterned graphene, can achieve absorption over 90% from 1.04 THz to 5.51 THz and relative bandwidth of up to 136.5% under normal incidence. Its absorption bandwidth and absorption peak can be adjusted by changing the conductivity of V O 2 or the chemical potential of graphene. The physical mechanism of the absorber is analyzed in detail by the use of the impedance matching theory and the electric field distributions of the V O 2 layer and graphene layer. The proposed absorber, with polarization insensitivity and incidence angle of 30° for both TE and TM polarizations, may have potential applications in tunable sensors, modulators, and imaging.