Vanadium dioxide-based ultra-bandwidth/dual-narrowband switchable terahertz absorbers and sensing applications

In this paper, an ultra-bandwidth/dual-narrowband switchable metamaterial absorber (MMA) is proposed for bandwidth and dual-narrowband absorption in the terahertz (THz) band based on the phase transition properties of vanadium dioxide (VO₂). When VO₂ is in the metallic state, the MMAs can achieve more than 90% broadband absorption in the range of 3.98-10.42 THz, with an absorption bandwidth of 6.44 THz and a relative bandwidth of 89.44%, as well as the advantages of polarization insensitivity and wide-angle absorption. When VO₂ insulates, the MMAs can achieve 99% absorption at 7.36 and 11.64 THz, realizing the double narrowband absorption function. As a sensor, simulation results show the sensitivity (S), quality factor (Q), and quality factor (FOM) at 11.64 THz of 0.2 THz/RIU, 29.6, and 5.92RIU^-1. The device has a wide- and narrowband integrated design with ultra-high absorption efficiency and can be applied in frontier fields such as terahertz stealth coating, biomolecular fingerprinting, and 6G communication band filtering.