Analysis of an ultra-broadband terahertz metamaterial absorber

Abstract

This paper introduces a metamaterial absorber (MA) based on vanadium dioxide (VO2) that achieves over 90% absorption of incident terahertz (THz) waves in between 4.50 THz to 11.90 THz with an average absorption of 94.64% and a relative absorption bandwidth (RAB) of 90.18% — the highest reported absorption bandwidth for VO2-based absorbers to our knowledge. The proposed metamaterial absorber features a design with a central square surrounded by four ’T’-shaped elements on each side, symmetrically arranged on a TOPAS dielectric substrate. We perform all numerical analyses keeping the phase-changing material VO2 in the metallic state, and our simulation results show that the design and optimization of the structural parameters contribute considerably to achieving a higher bandwidth. The physical mechanism underlying the absorber’s performance is analyzed using interference cancellation and impedance matching theory, with electric-field distributions observed at various frequencies to evaluate the absorber’s performance. The design offers a wide tunable range from 2% to 98% and is achieved by varying the conductivity of VO2 from 200 S/m to 2 × 105 S/m, enabling reconfigurable functionalities that are crucial for adaptable metamaterial absorbers. Furthermore, the absorber demonstrates polarization insensitivity and effective wide-angle absorption for transverse electric (TE) and transverse magnetic (TM) modes. With its high bandwidth, polarization insensitivity, and tunability features, the proposed design is promising for a range of THz applications, such as in modulation, sensing, and imaging technologies.