Towards chiral polaritons

Coupling between light and material excitations underlies a wide range of optical phenomena. Polaritons are eigenstates of a coupled system with hybridized wave function. Owing to their hybrid composition, polaritons exhibit at the same time properties typical for photonic and electronic excitations, thus offering new ways for controlling electronic transport and even chemical kinetics. While most theoretical and experimental efforts have been focused on polaritons with electric-dipole coupling between light and matter, in chiral quantum emitters, electronic transitions are characterized by simultaneously nonzero electric and magnetic dipole moments. Geometrical chirality affects the optical properties of materials in a profound way and enables phenomena that underlie our ability to discriminate enantiomers of chiral molecules. Thus, it is natural to wonder what kinds of novel effects chirality may enable in the realm of strong light-matter coupling. Right now, this field located at the intersection of nanophotonics, quantum optics, and chemistry is in its infancy. In this Perspective, we offer our view towards chiral polaritons. We review basic physical concepts underlying chirality of matter and electromagnetic field, discuss the main theoretical and experimental challenges that need to be solved, and consider novel effects that could be enabled by strong coupling between chiral light and matter.