▎ 摘　　要

A tunable broadband terahertz (THz) absorber based on vanadium dioxide (VO2) and graphene is proposed. The absorber, consisting of the VO2 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 VO2 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 VO2 layer and graphene layer. The proposed absorber, with polarization insensitivity and incidence angle of 30 degrees for both TE andTMpolarizations, may have potential applications in tunable sensors, modulators, and imaging. (C) 2021 Optical Society of America