The circular disk dual-notch multifunctional metasurface sensor based on the theory of bound states in the continuum

The integration of metasurfaces with optical sensors can effectively reduce the sensor volume and enhance its capability for electromagnetic field manipulation. This paper proposes and fabricates an all-dielectric multifunctional metasurface optical sensor based on a disk-with-double-gap silicon array on a quartz substrate. By introducing two asymmetrically arranged gaps oriented at 45° to break the structural symmetry, the proposed structure successfully converts the non-radiative ideal bound state in the continuum (BIC) into a high-Q quasi-BIC state with strongly localized optical fields, and excites an ultra-narrow linewidth Fano resonance sensing peak at 1617 nm. Simulation results indicate that the resonance peak is predominantly contributed by the magnetic dipole (MD) mode, with a theoretically maximum quality factor (Q) of up to 1.6×1051.6×10⁵ and a figure of merit (FOM) reaching 36350. The sensor exhibits a refractive index sensitivity of 363.5 nm/RIU and a temperature sensitivity of 51.96 pm/°C. Furthermore, the modulation depth of the metasurface resonance peak can be controlled by varying the polarization state of the incident light. Experimental sensing analysis demonstrates a sensitivity of 268.7 nm/RIU for liquids with different refractive indices. This structure holds promise for applications in environmental monitoring, biomedical detection, polarization-controlled optical switching, and provides a reference for multi-parameter metasurface sensors, extending the multifunctionality of metasurfaces in practical sensing applications.