Tunable broadband terahertz absorber based on a simple design of a vanadium dioxide resonator

A tunable broadband terahertz absorber based on five square rings of vanadium dioxide (VO₂) is proposed in this paper. We use a CST software to simulate the absorption characteristics of the absorber. The results show that the bandwidth of the absorber, with absorption exceeding 90%, reached 2.51 THz from 2.71 to 5.22 THz. The electric and surface current distributions reveal that the high absorption is due to the dipole resonance and coupling of the square rings. The absorption peak can be approximately tuned from 2% to 99.5% by varying the conductivity of VO₂ from 200 S/m to 200,000 S/m. In addition, the absorber has polarization insensitivity and can maintain good absorption performance over a wide range of incident angles. The designed absorber is expected to be widely used in areas of terahertz communication, imaging, and detection.