Hollow-structured all-silicon terahertz metasurface supporting quasi-bound states in the continuum for refractive index based Auramine O concentration sensing

Quasi-bound states in the continuum (QBIC), with exceptionally high- Q factors and the local field enhancement effect, have found potential applications in matter sensing. Introducing the QBIC mechanism into terahertz (THz) metasurfaces can significantly enhance the interaction between incident THz waves and matter, providing a feasible platform for the detection of biochemical substances. Currently, most experimental studies on terahertz QBIC metasurfaces utilize metallic structures. By contrast, research on terahertz all-dielectric QBIC metasurfaces generally remains at the simulation stage due to the high fabrication process requirements, and transitioning to the experimental stage still poses many challenges. In this paper, a hollow-structured all-silicon metasurface supporting THz QBIC is proposed. The resonance of THz QBIC is excited via a simple hollow structure and observed in experiment. Simulations and experimental results demonstrated that the designed THz QBIC metasurface can achieve sensing of Auramine O. Notably, it is the first study, to our knowledge, to employ a metasurface to sense Auramine O. Additionally, the sensing performance maintains good stability under different humidity and temperature conditions. This study provides new references and insights for the design and implementation of THz QBIC, and also opens a new pathway for the detection of Auramine O.