Ultrasensitive biosensor based on a terahertz metasurface

Recently, metamaterial-based biosensors have shown great promise as platforms for terahertz detection that is extremely sensitive. In this work, we present a novel H-split terahertz metasurface that is enabled by structural asymmetry to support a quasi-bound state in the continuum (QBIC) mode as well as an electric dipole resonance. The metasurface outperforms a number of previously published results with a sensitivity of 800 GHz/RIU on TPX and 150 GHz/RIU on silicon substrates. By shifting the central gap, a QBIC mode is created to improve sensing performance even more. This results in a high normalized figure of merit Q / V eff and a sensitivity of 900 GHz/RIU because of strong field confinement. With a detection limit as low as 0.031 mg/mL, experimental verification using bovine serum albumin validates the high sensitivity of both modes. The dual-mode behavior provides more robustness and design flexibility by combining high- Q QBIC resonance with broadband electric dipole sensing. These results demonstrate that our H-split metasurface is a highly efficient and adjustable platform for future integrated photonic applications and ultrasensitive terahertz biosensing.