Near-infrared Fano resonance in asymmetric silicon metagratings

Abstract

Recent progress on dielectric metasurfaces enables versatile flat optics designs including high-quality resonators. In this paper, we propose a high-quality resonator design based on asymmetric silicon metagratings in the near-infrared region. The design breaks the symmetry of a silicon subwavelength grating to manifest the dark mode of bound states in the continuum, resulting in a high-quality Fano resonance. Our numerical calculations indicate that its quality factor and peak wavelength are highly variable with different dimension parameters. Based on these results, we employ the metagrating resonator design for background index sensing with high sensitivity. Since it only consists of a glass substrate and a silicon layer of subwavelength thickness, this design can be a convenient platform for miniaturizing various resonator applications over large areas.