Tunable and switchable terahertz absorber based on photoconductive silicon and vanadium dioxide

In this paper, a tunable and switchable absorber based on photoconductive silicon (Si) and vanadium dioxide (VO2) is proposed. The designed absorber can achieve tunable bifunctional single-/dual-band absorption and switchable perfect absorption, by optically pumped silicon and temperature controlled VO2 individually or simultaneously. The absorption mechanism is explained by relative impedance theory. Moreover, a multiple interference model based on quasi-Fabry-Pérot cavity resonance is established to further reveal the principle of absorption, and the theoretical result is in good agreement with the numerical ones. Influence of structural parameters, polarization and angle of incident wave on absorption performances are systematically studied. The flexible tunable characteristics and polarization insensitivity of the designed absorber for multi-dimensional operation has potential applications in dynamic terahertz (THz) devices.