Radiative decay of incoherent excitons in the collective strong coupling regime

Molecular polaritons are hybrid light-matter states that emerge when the collective coupling between a large ensemble of molecules and a confined electromagnetic mode of an optical cavity exceeds all dissipation rates. Organic exciton polaritons are particularly interesting systems since strong coupling between electronic and vibrational degrees of freedom (DoF) gives rise to intricate relaxation processes that allow for population transfer between dark and polariton states, a feature which plays a central role in polariton-assisted remote energy transfer, modifications in photochemistry, polariton transport, and polariton condensation. To address their description, we recently introduced a formalism called collective dynamics using truncated equations (CUT-E). First, it exploits permutational symmetry for an efficient representation of the system. Second, it provides a simple solution to the problem for large N by deriving an exact solution in the N → ∞ limit and subsequently carrying out systematic 1/N corrections. Here I present how this formalism can be used to rigorously derive radiative decay rates from incoherent excitons. We characterize two main mechanisms: (1) Radiative pumping, where fluorescence into polariton modes can either escape the cavity or be reabsorbed by the molecules (photon recycling); and (2) Polariton-assisted Raman scattering, which involves the virtual emission of a photon followed by Raman scattering off a second molecule.