Quasi-BIC enabled all dielectric metasurface for dual parameter sensing and optical switching

In recent years, bound states in the continuum (BIC) in all-dielectric metasurfaces have emerged as a promising platform for realizing ultra-high- Q resonances, thereby facilitating the development of high-performance multifunctional photonic devices. In this study, we present a refractive index (RI) sensor based on an all-dielectric metasurface, featuring amorphous silicon (a-Si) nanostructures placed on a SiO 2 substrate. By introducing structural asymmetry, a quasi-BIC state is excited, producing a sharp Fano resonance with strong field confinement in the near-infrared region. The resonance exhibits a high Q factor of 3.11×10 4 . The optimized structure achieves a sensitivity of 485nmRIU −1 and figure of merit (FOM) of 11,040RIU −1 , confirming its excellent refractive index sensing performance. Furthermore, bidirectional optical switching can be achieved by tuning the polarization direction of the incident light. Numerical simulations also reveal that the quasi-BIC resonance is highly responsive to temperature variations, enabling dual-parameter sensing capability. These results help us better understand BICs and present a promising approach for developing advanced photonic devices, including optical switches and sensors.