Tunable perfect absorption and versatile applications based on a simple black phosphorus metasurface in terahertz

In this study, we introduce a simple black phosphorus (BP) metasurface consisting of a square BP sheet placed on a silicon substrate. The proposed metasurface achieves perfect absorption through guided modes, with an absorbance spectrum peaking at 99.85 % for an electron doping concentration of 0.8 x 1018 m- 2. We demonstrate the tunability of the absorbance spectrum using polarization angles and electron doping concentrations, as evidenced by finite-difference time-domain (FDTD) simulations and coupled-mode theory (CMT) calculations. Furthermore, we assess the sensing capabilities of BP-based metasurface, achieving a maximum sensitivity of 120.1 GHz/RIU. Additionally, we investigate the slow-light effect at various electron doping concentrations, reaching a maximum group index of 149924. This work provides valuable insights into the potential practical applications of BP-based metasurface and contributes to the advancement of sophisticated optical devices.