Molecular polaritonics in dense mesoscopic disordered ensembles

We study the dependence of vacuum Rabi splitting (VRS) on frequency disorder, vibrations, near-field effects and density in molecular polaritonics. In mesoscopic limit, static disorder alone can already introduce a loss mechanism from polaritonic states into dark state reservoir, which we quantitatively describe, providing an analytical scaling VRS with level disorder. Disorder additionally split ensemble donor-type acceptor-type molecules combination vibronic coupling, dipole-dipole interactions vibrational relaxation induces incoherent FRET (F\"{o}rster resonance energy transfer) migration excitations within collective state. This is equivalent to dissipative has effect saturating even reducing mesoscopic, high-density limit. Overall, this analysis allows quantify crucial role played by cavity quantum electrodynamics disordered ensembles.