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arXiv · 2604.01772

Ultrasensitive Terahertz Metasurface Biosensor Based on Quasi-Bound States in the Continuum

Junhui Guo·Bing Dong·Eryong Zhang·Qing-An Tu·Xiaoyong He·Xichuan Wu·Mingjing Liu·Maohua Gong·Yan Meng·Xiang Xi·Hongcheng Wang·Zhen Gao
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Abstract

The terahertz (THz) spectral regime offers unique opportunities for next-generation biochemical sensing due to its non-destructive, label-free probing capability and strong sensitivity to molecular vibrations. However, conventional THz biosensors remain hampered by intrinsically low-quality factors and limited sensitivity, severely restricting their utility for trace-level biochemical and chemical detection. Here, we report an ultrasensitive THz metasurface biosensor that harnesses quasi-bound states in the continuum (QBICs) with sharp resonances and enhanced light-matter interactions to overcome these limitations. As a proof of concept, the device achieves label-free detection of a sulfur-containing amino acid cysteine, with an ultrahigh sensitivity of 492 GHz/RIU and an ultralow detection limit down to 0.00025 mg/mL. The synergy between QBIC-induced field confinement and meticulous structural optimization of the metasurface underpins this performance, marking a significant advance over conventional THz metasurface biosensing schemes. These results establish QBIC-based metasurfaces as a promising platform for ultrasensitive and high-precision biochemical and chemical sensing, with broad implications for medical diagnostics, food safety, and environmental monitoring.

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Junhui Guo, Bing Dong, Eryong Zhang, Qing-An Tu, Xiaoyong He, Xichuan Wu, Mingjing Liu, Maohua Gong, Yan Meng, Xiang Xi, Hongcheng Wang, Zhen Gao. 2026-04-02. Ultrasensitive Terahertz Metasurface Biosensor Based on Quasi-Bound States in the Continuum. https://doi.org/0.1002/lpor.202503194

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