An all-dielectric metasurface based on Fano resonance with tunable dual-peak insensitive polarization for high-performance refractive index sensing.

A symmetric all-dielectric metasurface based on silicon and GaAs is proposed and numerically studied. In the mid-infrared region, two Fano resonant peaks with a reflectance exceeding 90% are observed. By altering the geometric parameters of the metasurface, the wavelength location and quality factor (-factor) of the resonant peaks can be tuned. The highest -factors can be 9609.67 and 3476.33, respectively. The proposed metasurface structure for optical refractive index sensing shows high performance and is insensitive to the plane wave's polarization state. In the refractive index range of 1.00 to 1.10, the highest sensitivity and figure of merit (FoM) are 1901.34 nm RIU and 2492.04 RIU, respectively. The highest sensitivity is 2248.57 nm RIU and FoM is 977.64 RIU in the refractive index range of 1.30 to 1.40. These research results will help improve and innovate related sensing technologies and devices.