Polaritonic Spectra of Optical Mie Voids

ABSTRACT The progress in understanding the optical and microscopic properties of polaritons relies on various optical cavities to confine electromagnetic radiation, which causes a demand for new platforms with higher ‐factors and better fabrication robustness. In this context, so called Mie voids—spherical cavities inside a dielectric medium, where the light confinement occurs due to refractive index contrast at the air‐dielectric interface—present a substantial interest. Here, we theoretically study the resonant characteristics and polaritonic spectra of spherical Mie cavities loaded with resonant media, as well as address the inverted problem, where a Mie void is formed inside a resonant dispersive medium. We establish approximate analytical expressions for the ‐factors of Mie void cavities, find the parameter ranges of spherical voids leading to the regimes of weak and strong light–matter coupling, and analyze the concomitant effects, such as ‐factor enhancement and spatial field localization, from the polaritonic perspective. Our result could be valuable for the design of new polaritonic systems.