A perfect absorber based on a VO2-tunable Fabry-Perot cavity: An analysis of periodic oscillation absorption characteristics

Terahertz metamaterial absorbers (TMAs) have garnered significant attention as vital electromagnetic wave-absorbing devices. In this study, we designed a terahertz metamaterial absorber (TMA) utilizing an asymmetric Fabry-Perot nanocavity comprising vanadium dioxide (VO2), gold (Au), and polyimide. The TMA exhibits five perfect absorption peaks within 0.1 THz to 10 THz, with an absorption rate exceeding 97%, peaking at 99%. The absorption rate oscillates periodically between 0 and 1, and its oscillating absorption peak can be determined by fm(fm = (2m + 1)c0/(4t√ε2), while tunability of the absorption rate between 15% and 97% is achievable by adjusting the conductivity of (VO2) (2 × 102 ∼2 × 105 S/m). The physical mechanism of the absorption peak was analyzed by simulation and compared with theoretical analysis. The results show that the absorption peak of the absorber's absorptivity can be insensitive to polarization and has a wide absorption angle of 80% up to 40° or more. Importantly, the thickness of the absorber (VO2) layer can be calculated from the desired absorption frequency and dielectric constant of the interlayer medium,d=√(ε0 /µ0) /σ , thus reducing the need for redesigning different resonant layer patterns. This work provides a new perspective on terahertz absorber design.