# Quasi-Bound States in the Continuum-Enabled Wideband Terahertz Molecular Fingerprint Sensing Using Graphene Metasurfaces

## TL;DR

A new THz metasurface sensor using graphene enhances molecular detection by amplifying specific absorption signals for precise and sensitive sensing.

## Contribution

A tunable graphene metasurface platform using Quasi-BIC resonance for enhanced THz molecular fingerprint detection is introduced.

## Key findings

- Quasi-BIC resonance peaks were tuned to match lactose and tyrosine absorption lines in the THz range.
- Absorption peak intensity was enhanced 763-fold for 0.1 μm thick analytes compared to conventional methods.
- The sensor shows high sensitivity and potential for biomedical and food safety applications.

## Abstract

The unique molecular fingerprint spectral characteristics in the terahertz (THz) band provide distinct advantages for non-destructive and rapid biomolecular detection. However, conventional THz metasurface biosensors still face significant challenges in achieving highly sensitive and precise detection. This study proposes a sensing platform based on quasi-bound states in the continuum (Quasi-BIC), which enhances molecular fingerprint recognition through resonance amplification. We designed a symmetric graphene double-split square ring metasurface structure. By modulating the Fermi level of graphene, this system generated continuously tunable Quasi-BIC resonance peaks across a broad THz spectral range, achieving precise spectral overlap with the characteristic absorption lines of lactose (1.19 THz and 1.37 THz) and tyrosine (0.958 THz). The results demonstrated a remarkable 763-fold enhancement in absorption peak intensity through envelope analysis for analytes with 0.1 μm thickness, compared to conventional bare substrate detection. This terahertz BIC metasurface sensor demonstrates high detection sensitivity, holding significant application value in fields such as biomedical diagnosis, food safety, and pharmaceutical testing.