Maximally Chiral Emission via Chiral Quasibound States in the Continuum

Abstract

Although numerous natural materials exhibit chiral optical phenomena, they are typically very weak. Chiral nanophotonic structures can significantly enhance the chiroptical responses and provide unprecedented design flexibility. However, achieving extreme chirality that approaches the ultimate theoretical limit remains challenging. Here, chiral quasibound states in the continuum are realized in the visible range, and maximally chiral emission from a perovskite metasurface is demonstrated. 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 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. The physical mechanism is explained using the reciprocity principle. Approaching the ultimate limit of chiral responses may lead to far-reaching consequences in various important applications as well as fundamental studies.

Emission Control in Metal Halide Perovskite Lasers

“…Polarization control in perovskite lasers, especially circularly polarized emission, is still in the early stages and needs more research attention. Upon introducing the concept of a metasurface into perovskite structures, chiral spontaneous emission from perovskites has been reported by several research groups. − Circularly polarized lasing emission with large chirality and high quality factor shall be explored in a perovskite system in the future.…”

Chiral electroluminescence from thin-film perovskite metacavities

“…Recently, chiral light sources based on perovskite materials have attracted considerable attention to fully exploit their exceptional material properties. Extensive research has been conducted to obtain chiral PL from perovskite materials (27)(28)(29)(30)(31)(32)(33)(34)(35). For example, chiral perovskite materials can be created by incorporating chiral organic ligands on the surface of perovskite crystals or intercalating chiral organic cations into the perovskite lattice (27)(28)(29).…”

Enhancing Circularly Polarized Emission by a Planar Chiral Dielectric Metasurface

“…Resonant dielectric metasurfaces have also been explored to enhance CPE due to their advantages of low material loss and high Q. Metasurfaces created by periodic arrays of chiral dielectric antennas with 3D chirality were shown to support chiral quasi-BICs with large Q values. [32][33][34][35][36] Recently, a highly circularly polarized laser output was demonstrated based on a chiral quasi-BIC. [37] However, these chiral metasurfaces are not rigorously planar (the structure is varied along the normal direction) and may cause inconvenience in their fabrication process.…”