Design of metasurface absorber with four unequal rectangular rings for ultrawide THz bandwidth

Abstract In this paper, a metamaterial absorber (MA) is proposed based on vanadium dioxide (VO 2 ) having high absorption performance and high bandwidth in terahertz (THz) frequency range. The proposed metamaterial absorber has absorption efficiency over 90% in the frequency range between 2.45 THz to 7.23 THz with a bandwidth of 4.78 THz and average absorption rate is 95.88% and the relative absorption bandwidth (RAB) is of 98.76%. The proposed metamaterial absorber features a design with four rectangular rings of VO 2 symmetrically arranged on SiO 2 dielectric substrate. We perform all numerical analyses keeping the phase-changing material VO 2 in the metallic state. Our simulation results demonstrate that a larger bandwidth can be achieved in a significant way through structural parameter design and optimization. In order to determine the absorption performance of the proposed absorber, the electric-field distributions at different frequencies are observed, and the physical process underlying the absorber’s performance is examined using interference cancellation and impedance matching theory. By adjusting the conductivity of VO 2 from 200 S m −1 to 2 × 10 5 S m −1 , the design provides a broad tunable range from 6% to 100%, enabling reconfigurable features that are essential for flexible metamaterial absorbers. Additionally, for transverse electric (TE) mode and transverse magnetic (TM) mode polarizations, the absorber exhibits effective wide-angle absorption and polarization insensitivity. With its high bandwidth, polarization insensitivity, and tunability features, the proposed design is promising for a certain range of THz applications, such as in sensing and imaging technologies.