Double-layer Terahertz Absorber Based on the Vanadium Dioxide and Cavity Resonance

In this paper, a double-layer terahertz (THz) absorber based on the vanadium dioxide (VO2) and cavity resonance is proposed, which can obtain wide-band tunability while broadening the absorption band greatly in THz band. When the temperatures (t) reaches 350 K, VO2 exhibits metallic property. In such a case, the calculated results show that the absorption bandwidth (absorption is over 0.9) of the proposed absorber can cover 4.97-9.03 THz and its relative bandwidth (RB) can reach 58%. And for TM wave, the absorption ranges from 5.09 THz to 9.07 THz and its RB arrives at 56.21%. When VO2 is in the low temperature (t = 300 K), it appears dielectric property and the multi-frequency absorption phenomenon can be observed. Two operating states can be realized by tailoring the ambient temperature. The absorption mechanism of the proposed absorber also is analyzed through the electric field and surface current diagrams. Compared with the conventional tunable absorber, the presented absorber provides the great application prospect for the flexible and temperature-controlled absorbers.