Ultra-wideband terahertz metamaterial absorber with polarization insensitivity and broad incidence angle absorption

Terahertz metamaterials absorbing materials (TMAs) are a subject of interest due to their capacity to absorb specific electromagnetic waves. This study proposes an ultra-wideband perfectly absorbing metamaterial absorber (MMA) with polarisation insensitivity and wide incident absorption angle for the terahertz (THz) band. The TMA employs vanadium dioxide(VO2) as the resonant layer, obstructing electromagnetic waves from traversing the metamaterial via a gold substrate to create a straightforward Fabry-Perot asymmetric resonant cavity and broadening the bandwidth through the incorporation of a square frequency selective surface (S-FSS) array. The experimental simulations demonstrate that the TMA exhibits an ultra-wide absorption bandwidth of 9.54 THz, with up to 90% absorption within the 2.9-12.44 THz range. Furthermore, the tunability of VO2 conductivity has been leveraged to achieve a controllable absorption range of 5%-99%. The incident angle sensitivity of TMA to TE and TM polarisation was subjected to further investigation. It was observed that the TMA can sustain a relative bandwidth exceeding 66% and an absorption rate surpassing 90% in the 60 degrees region. Additionally, it can achieve a relative bandwidth of up to 129.4% at an incidence angle of 40 degrees. It can therefore be concluded that the perfect absorber with ultra-wide absorption bandwidth, as designed in this study, has potential applications in optical tunable absorber devices and other fields.