Angular Transmission Response of In-Plane Symmetry-Breaking Quasi-BIC All-Dielectric Metasurfaces

High-index dielectric metasurfaces have gradually become one of the most promising platforms in the field of nanophotonics due to the ease in engineering their optical behavior and their small size. Several numerical and experimental studies have been conducted in the fields of plasmonic metasurfaces and dielectric metasurfaces on in-plane symmetry-breaking nanodisk metasurfaces supporting high-Q states called "quasi-BICs", where these devices are useful for applications such as imaging and biodetection. This article studies numerically and experimentally symmetry-breaking metasurfaces made of amorphous silicon (α-Si) nanodisks in the visible-to-near-infrared range. It is reported that the angular response of the quasi-BICs for type I symmetry-breaking metasurfaces can be blue-shifted with respect to incident light tilted parallel to the axis of mirror symmetry and red-shifted when tilted perpendicular to it due to changes in the in-plane momentum. Comparatively, the angular response of the quasi-BICs of type II symmetry-breaking metasurfaces can only be red-shifted due to mirror symmetries in both axis directions.