An ultra-broadband and multi-frequency switchable terahertz absorber based on a patterned VO₂ multilayer stacked...

This study presents the design of a multilayer stacked ultra-broadband and multi-frequency switchable terahertz absorber employing vanadium dioxide (VO₂), polydimethylsiloxane (PDMS) and embedded gold (Au). This absorber achieves reversible phase transitions in VO₂ through temperature control, consequently altering its electrical conductivity to switch absorption characteristics. Based on impedance matching theory and simulations of electric field and current distribution, the physical mechanism enabling ultra-broadband and multi-frequency switching in this VO₂ switchable terahertz absorber is elucidated. Simulation results demonstrate that the absorber realizes ultra-broadband absorption, exhibiting a bandwidth of 6.36 THz spanning from 6.47 THz to 12.83 THz at a metallic-phase conductivity of 8 × 10⁴ S m^-1 for VO₂. In contrast, an insulating-phase conductivity of 150 S m^-1 for VO₂ enables the absorber to exhibit pronounced multi-frequency absorption properties, where six strong absorption peaks with absorption rates over 90% are observed, corresponding to the absorption frequency points of 3.26 THz, 6.68 THz, 7.69 THz, 9.26 THz, 10.32 THz and 13.09 THz, respectively. Furthermore, by employing a symmetrical structural design, this absorber exhibits outstanding polarization stability and retains highly efficient absorption across a broad range of incident angles spanning from 0° to 60°. Therefore, this absorber demonstrates tremendous prospects in cutting-edge fields such as terahertz imaging, terahertz modulation, and material inspection.