Refractive index sensor based on quasi-BIC-excited metal-dielectric hybrid metasurfaces

Bound states in the continuum (BICs) present a key breakthrough direction for high-performance optical sensors, attributed to their infinitely high quality factor (Q) and continuously tunable resonance intensity. By introducing symmetrical defects to transform BICs into quasi-BICs (q-BICs), ultra-high Q factor can be achieved. In this work, we engineered a symmetry-protected BIC mode within a metal-dielectric metasurface, exciting sharp resonant absorption in the near-infrared regime. Numerical simulations demonstrate that the proposed sensor achieves a sensitivity of 862.4 nm/RIU with a Q factor approaching 300. These results suggest significant potential for applications in photonic biosensing and environmental monitoring.