Tunable dual-broadband terahertz absorber based on vanadium dioxide stacked with multilayer structures

This study presents a tunable dual-broadband terahertz absorber, which is constructed utilizing alternating layers of square vanadium dioxide and Topas dielectric, with a metallic reflector at its base. The simulation results demonstrate that this absorber achieves 90% absorption bandwidths of 1.58 THz and 1.59 THz across the frequency ranges of 0.58-2.16 THz and 3.38 to 4.97 THz, respectively. By thermally adjusting the conductivity of vanadium dioxide, the absorption peaks can be tuned continuously between 2.6% and 99%. The mechanisms behind perfect and dual-broadband absorption are examined through impedance matching theory and electric field current distribution analysis. Owing to its symmetrical design, the absorber exhibits polarization insensitivity and excellent wide-angle performance. Additionally, by varying the thickness of the dielectric layers, the dual-broadband absorption can be converted into ultra-broadband absorption with a 5.3 THz bandwidth, maintaining stable performance over a wide incidence angle from 0 degrees to 60 degrees. This absorber design shows significant potential for applications in terahertz imaging, material detection, and stealth technology.