Quantifying the Number of Dark, Gray, and Bright States as a Function of the Spectral Overlap in Polaritonic Systems

Strong exciton-photon coupling can steer photophysical processes. However, the picture where it leads to two polaritonic states and a manifold of optically dark states is now questioned. Instead, a picture where inhomogeneous broadening results in a partial photonic contribution to the dark states has gained ground. To understand the consequence of these dark and so-called gray states, they first need to be experimentally quantified. Here we use angle-resolved emission, coupled to rate equation modeling, to quantify the absolute number of states in optical cavities. In addition, we also estimate the fraction of states that are gray by means of computer simulations. We find that the number of gray states is proportional to the overlap between the energy of the dark and polaritonic states. This knowledge can be applied to all previous and future studies to interpret how detuning affects the relative number of dark and gray states and, consequently, polaritonic dynamics.