Narrow Fano resonances in Si nanocylinder metasurfaces: Refractive index sensing

Abstract

All dielectric metasurfaces are attracting great attention for their potential to control light reflection and transmission at the nanoscale. Here, we make use of a coupled electric/magnetic dipole formulation for a periodic array of high-refractive-index cylinders to analytically explore the emergence of Fano resonances for both s- and p-polarized waves. Strong Fano resonances with large Q-factors are found in Si nanocylinder metasurfaces as a result of the lattice-induced interplay between electric and magnetic dipole resonances, where the narrow resonances are connected to bound states in the continuum supported by the lattice. The impact on the refractive index of the surrounding medium is analyzed, revealing that such simple all dielectric metasurfaces are suitable for refractive-index sensing devices with figures of merit of two orders of magnitude.