Dual-band Terahertz Fano Resonance in Asymmetric Split Rectangular Resonator for Label-free Detection

Inhalt:
A dual-band terahertz metasurface biosensor is proposed and experimentally validated for high-sensitivity, label-free detection. The metasurface consists of a pair of asymmetric split rectangular resonators coupled with a central circular disk, enabling two distinct resonant modes via distinct electromagnetic interactions. The first resonance at 1.84 THz originates from a localized surface plasmon resonance (LSPR) confined to the circular disk and symmetrically coupled to the surrounding resonator pair. The second resonance, centered at 3.08 THz, is attributed to Fano interference between a high-order asymmetric mode of the split rectangular resonators plasmonic excitation. Simulated refractive index sensitivities reach 382.28 GHz/RIU and 616.30 GHz/RIU for the respective modes. Experimental measurements using 293T cells reveal detection sensitivities of 350 kHz/(cell·mL^-1) and 790 kHz/(cell·mL^-1), confirming the metasurface’s potential in dual-mode biosensing applications.