This study presents a tunable far-infrared (FIR) metamaterial absorber integrating vanadium dioxide (VO 2 ) and graphene to achieve dynamic switching between ultra-broadband and narrowband absorption. The proposed absorber leverages the insulator-to-metal transition of VO 2 and the tunable conductivity of graphene to modulate absorption characteristics in the FIR region (13.8–29.1 µm). When VO 2 is in its metallic state, the absorber achieves over 90% absorptance across a broadband range, while in the insulating state, it exhibits a narrowband absorption peak at 17 µm with 97.86% absorptance. The design incorporates a titanium cylinder, a patterned graphene layer, an SiO 2 dielectric with embedded VO 2 cross strips, and a gold substrate. Electromagnetic simulations using the finite-difference time-domain method, combined with impedance matching theory and electric field distribution analysis, elucidate the absorption mechanisms. The proposed absorber offers active tuning via both electrical and thermal stimuli, enabling broadband perfect absorption for infrared stealth, narrowband resonance for biosensing, and reversible temperature-triggered optical switching.
Cao et al. (Mon,) studied this question.