Chiral emission from perovskite metasurfaces via chiral quasi-bound states in the continuum

Abstract

Chiral nanophotonic structures can significantly enhance the chiral optical responses and provide unprecedented design flexibility. However, achieving extreme chirality that approaches the ultimate theoretical limit remains challenging. Here, chiral quasi-bound states in the continuum are realized in the visible range by controlling the etching depths in the substrate and inducing out-of-plane symmetry breaking. A perovskite film is spin-coated on a patterned glass substrate. Grayscale lithography is employed to control the etching depths in the substrate and induce out-of-plane symmetry breaking. An extremely high level of chiral emission from the perovskite metasurface is experimentally achieved in the normal direction at room temperature. Chiral emission is maximally enhanced for one helicity via critical coupling while strongly suppressed for the other helicity. Approaching the ultimate limit of chiral interactions may lead to far-reaching consequences in a variety of important applications.