A Multifunctional Terahertz Metadevice Enabled by Single-Layer VO2 : From Ultra-Broadband to Dual-Narrowband Perfect Absorption

Terahertz (THz) metamaterial absorbers are critical for imaging, stealth and communication applications, yet it remains a key challenge to realize reversible switching between ultra-broadband and dual-narrowband perfect absorption in a single compact device. Here, we propose a switchable THz metamaterial absorber enabled by a single vanadium dioxide (VO₂) layer, which achieves flexible mode switching via the insulator-metal phase transition of VO₂. When VO₂ is in the metallic state, the absorber realizes over 90% absorption in 4.10-12.58 THz, with an absolute bandwidth of 8.48 THz and a relative bandwidth of 101.67%, as well as excellent polarization insensitivity and wide incident angle tolerance. When VO₂ is in the insulating state, it achieves dual-narrowband perfect absorption at 4.69 THz and 11.51 THz, with peak absorption rates up to 99.6% and 99.9%, respectively. The absorption mechanism is systematically analyzed via impedance matching theory and geometric parameter optimization. This work provides a simple and effective design strategy for multifunctional THz devices, with broad application prospects in THz imaging, stealth and intelligent communication systems.