Quasi-bound states-driven terahertz molecular fingerprint retriever

Limited by the weak resonant intensities of ordinary modes, the sensitivity of terahertz sensing is often insufficient to retreive trace molecular fingerprint features. Here, a quasi-bound states in the continuum-induced terahertz metasurface with high field enhancement is proposed to achieve trace molecular fingerprint sensing. The ratio of radiative loss to intrinsic loss of proposed metasurface can be accurately tailored by controlling in-plane symmetry, enabling working in the under-coupled, critically coupled and over-coupled regions. Based on the proposed metasurface, a pixelated metasensor has been designed for molecular fingerprint reconstruction, where negative, near-zero, and positive signal modulations can be observed in three different coupling regions. Finally, we demonstrate that the designed pixelated metasensor can achieve quantitative sensing of mixtures, providing an alternative technique for detecting and identifying trace molecules.