Polarization-selective high-sensitivity Fano resonance in all-dielectric metasurface based on quasi-bound states in the continuum

The discovery of quasi-bound states in the continuum (Q-BIC) in optical micro and nanostructures has attracted widespread attention and has shown great potential in many optical applications. To address the growing demand for integrated lab-on-chip systems combining polarization control and high-sensitivity sensing, we propose a multifunctional all-dielectric metasurface that exploits Q-BICs to simultaneously achieve high-Q resonances, enhanced refractive index sensitivity, and strong polarization selectivity. The dominant contributions of magnetic dipole (MD) and magnetic quadrupole (MQ) in the resonant modes are verified through near-field analysis and multipole decomposition. Simulation results show that the metasurface exhibits highly sensitive sensing properties in the near-infrared band, with a resonance modulation depth close to 100 %, a maximum sensitivity of 439 nm/RIU, a figure of merit (FOM) of up to 921.18 RIU⁻¹, and a polarization extinction ratio of 54 dB. This research offers a novel metasurface design strategy based on the Q-BIC mechanism, enabling high-performance optical sensing and polarization control for near-infrared biosensing, molecular detection, and lab-on-chip integration.