Highly tunable rotationally symmetric multi-band terahertz absorber with enhanced sensing capabilities

In this study, we propose a novel multi-band absorber structure with exceptional tunability and high performance, aimed at applications in biosensing and medical diagnostics. The absorber consists of a three-layer design, including a gold bottom layer, a silicon dioxide middle layer, and a DSM top layer. The device achieves polarization insensitivity through a rotationally symmetric design, as verified by simulations under varying polarization angles. Six distinct absorption peaks (modes) were observed in the 4-10 THz range, with resonance frequencies and absorption rates demonstrating strong tunability through structural parameter adjustments and Fermi energy modulation. Specifically, by varying structural parameters, the absorption peaks can be fine-tuned, with mode-specific dependencies identified. Additionally, Fermi energy modulation provides an effective approach for shifting absorption peaks through changes in carrier concentration, demonstrating blue shifts across all modes. The absorber's sensing potential was evaluated in terms of its quality factor (<i>Q</i>) and refractive index sensitivity (<i>S</i>). The results reveal high performance, with a maximum refractive index sensitivity of 3752 GHz per RIU and a <i>Q</i>-factor of 132.76.