High sensitivity of a perfect absorber based on octagonal-star and circular ring patterned graphene metasurface

This study presents a triple-band terahertz tunable perfect absorber designed with an octagonal-star and circular ring monolayer graphene metasurface, noted for its tunability, polarization insensitivity, and high sensitivity. The graphene absorber was simulated using the finite element method and validated through impedance matching. Simulation results reveal three perfect absorption peaks at 5.5, 7.87, and 9.25 THz, with absorption rates reaching approximately 99% at 7.87 and 9.25 THz. Variations in the dielectric layer material, along with adjustments to the structural and intrinsic graphene parameters, were analyzed to optimize the efficiency of the triple-band absorption peaks. The simulations show that the structure’s high symmetry provides incident and polarization insensitivity, maintaining absorption rates above 98% over a broad range of incident and azimuth angles. The device’s sensing performance was evaluated by varying the ambient refractive index, achieving a maximum sensitivity (S) of 5.329 THz/RIU. These results indicate that this high-sensitivity sensor holds significant potential for applications in sensing, tunable spectral detection, and environmental monitoring.