Terahertz Broadband Adjustable Absorber Based on VO2 Multiple Ring Structure

A broadband adjustable absorber operating in the terahertz (THz) range is presented based on a vanadium dioxide (VO2) multiple ring structure with a certain gap design. The dynamic absorption regulation of the absorber is realized by utilizing the phase-change characteristics of VO2, which is easily affected by external temperature. The simulation results show that when the external temperature reaches 350 K, the conductivity of VO2 can reach 2 × 105 S/m, and the absorber can obtain an absorption efficiency of over 90% from 3.01 THz to 7.27 THz. At this time, the absorption bandwidth reaches 4.26 THz with 82.9% of the relative bandwidth. When the external temperature reaches 300 K, the conductivity changes to 200 S/m, and the absorption efficiency is less than 4%, indicating the strong THz absorption dynamic adjustable ability. Further, through analyzing the optimal impedance matching and the electric field distribution under different conductivities, the broadband absorption mechanism of the absorber can be obtained. Finally, this paper shows that the absorption spectrum cannot be influenced by small angle incidences in both polarization modes. Therefore, the ultra-wideband adjustable absorber is expected to have applications in the terahertz fields of detecting, modulating, and switching.