A Wideband Terahertz Absorbing Metasurface with Large Tuning Range Enabled by $\text{VO}_{2}$

In this paper, a tunable wideband terahertz (THz) metasurface (MS) absorber incorporating the phase changing characteristics of vanadium dioxide (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{VO}_{2}$</tex>) has been proposed and thoroughly investigated. The presented design achieves a very high absorption bandwidth of 5.83 THz, with over 90% absorbance in the frequency span of 6.59 THz to 12.42 THz under the metallic state of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{VO}_{2}$</tex>. Conversely, when <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{VO}_{2}$</tex> transitions in its insulating phase under thermal control, the suggested MS exhibits near complete reflection of the incoming wave with absorbance rate of merely 1.7 %; thereby demonstrating a large switching capability. It shows polarization insensitivity owing to its fourfold symmetry. Moreover, the MS absorber maintains of over <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{9 0 \%}$</tex> absorption efficiency for incident angles up to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm \mathbf{4 0}^{\circ}$</tex> under both transverse electric (TE) and transverse magnetic (TM) polarization. The power loss analysis results show that the top resonating layer made up of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{VO}_{2}$</tex> is primarily responsible for wideband absorption. The designed MS absorber holds great potential in various fields namely terahertz sensing, modulation, switching and many other futuristic 6 G applications.