Vanadium dioxide and graphene-based switchable and tunable terahertz absorber

A terahertz absorber with switchable and tunable absorption capabilities was proposed. The absorber comprises six layers including vanadium dioxide (VO₂), Topas layer, graphene layer, another VO₂ layer, another Topas layer and a gold layer as substrate. The absorption performance of the absorber is investigated using the time-domain finite-difference (FDTD) method. The results demonstrate that the absorber is capable of achieving single-band absorption from 0.98 to 3.92 THz or dual-band absorption from 1.51 to 3.45 THz and 7.0 to 8.35 THz via the phase change of VO₂ through temperature variation. In the case of dual-band absorption, it can even realize an absorption strength of 99 % within a bandwidth of 0.8 THz, demonstrating its excellent absorption performance. Additionally, the absorption rate of the absorber can be dynamically adjusted by tuning the graphene's Fermi level (E_F). Moreover, the physical principles of absorption are elucidated through impedance matching theory and transmission line theory. Furthermore, the effect of the incidence angle and polarization angle on absorption was studied and found that the structure is insensitive to two factors. The research paves the way for innovative designs of terahertz functional devices aimed at applications such as stealth, modulation, switching, and sensing within the terahertz frequency range.