Adjustable broadband absorber based on vanadium dioxide multiple coupled diagonally sliced square ring shaped structure for THz frequency

Abstract

A broadband absorber with multiple coupled diagonally sliced square rings at terahertz frequency using vanadium dioxide is proposed. The proposed structure exhibits more than 90 % absorption in the frequency range of 2.85–7.51 THz, with a relative bandwidth of 89.96 % and an absorption bandwidth of 4.66 THz. The absorptivity curve increases as vanadium dioxide conductivity rises from 200 S/m to 200,000 S/m, giving a wide range of tunability from 1.62 % to 100 % at 3.4 THz. Due to its geometrical symmetry, the proposed structure is independent of the polarization angle under normal incident plane waves. The proposed structure works for different incident angles for transverse electric (TE) mode and transverse magnetic (TM) mode with oblique incidence plane waves. The results demonstrate the broad bandwidth compared to the state-of-the-art designs within the same frequency band with potential applications in sensors, switches, tuning, and modulation in the terahertz range.