Triple-band tunable terahertz metamaterial absorber enabled by surface design of goggles-like structure using two identical VO2 square frames connected by a VO2 horizontal connecting strip

Abstract

Triple‑band tunable terahertz metamaterial absorber using goggles-like (GL) structure formed by two identical vanadium dioxide (VO2) square frames connected by a VO2 horizontal connecting strip is presented in this work, the GL structure deposited on SiO2 film and gold mirror forms the basic cell of triple-band absorption. Three discrete frequency points with near-perfect absorption are realized, and their physical mechanisms are discussed with the aid of near-field maps of these absorption peaks. Variations in structural parameters of GL are given, which show that the presence of VO2 horizontal connecting strip and its connection position are crucial in obtaining triple-band absorption. More importantly, amplitude of the triple-band absorption could be dynamically modulated that by changing the conductivity of VO2 from 20S/m to 20000 s /m. Absorption amplitudes of the three absorption peaks are actively tuned from near-perfect absorption to near-zero absorption. The modulation depth (MD) of the three absorption peaks are 0.996, 0.998, 0.999, respectively, and extinction ratio (ER) of them are − 33.02 dB, −25.15 dB, −29.51 dB, respectively. The proposed triple-band metamaterial absorber with excellent tunable characteristics (MD and ER) could have broad application prospects in the fields of modulation, switching, and imaging technology.