Continuum model of strong light-matter coupling for molecular polaritons

Strong coupling between light and matter generates hybrid polaritons. We present a continuum model that describes the polaritons by light and matter densities of states (DOS) that only depend on the refractive index of the material. This model is applied to molecular polaritons derived from molecules with broad spectral absorption. While the photonic DOS has a complex spectral distribution, the matter DOS is largely unmodified by strong coupling. We argue that bright states cannot be partitioned from dark states, and instead the photonic DOS is shared over a vast number of matter states.