Chiral Light in Twisted Fabry–Pérot Cavities

Fundamental studies of the interaction of chiral light with chiral matter are important for the development of techniques that allow handedness-selective optical detection of chiral organic molecules. One approach to achieve this goal is the creation of a Fabry–Pérot cavity that supports eigenmodes with a desired electromagnetic handedness. This paper theoretically studies chiral Fabry–Pérot cavities with mirrors comprising 1D photonic crystal slabs made of van der Waals As₂S₃, a material with one of the highest known in-plane anisotropies. By utilizing the anisotropy provided by As₂S₃, Fabry–Pérot cavities with constitutional and configurational chiralities are designed. It is demonstrated that in cavities with constitutional chirality, electromagnetic modes of left or right handedness exist due to the chirality of both mirrors, often referred to as handedness preserving mirrors in the literature. At the same time, cavities with configurational chirality support modes of both handednesses due to the chiral morphology of the entire structure, set by the twist angle between the optical axes of the upper and lower non-chiral anisotropic mirrors. The developed chiral Fabry–Pérot cavities can be tuned to any distance between the mirrors by properly twisting them, making such systems a prospective platform for the coupling of chiral light with chiral matter.