Strong light–matter coupling in microcavities characterised by Rabi-splittings comparable to the Bragg stop-band widths

The vacuum Rabi splitting of polaritonic eigenmodes in semiconductor microcavities scales with the square root oscillator strength, as predicted by coupled model and confirmed many experiments. We show here that law is no more applicable if becomes comparable or larger than stop-band width Bragg mirrors forming cavity. Once strength large enough, material hosting excitons hybridises quasi-continuum microcavity modes lying outside stop-band, thus a novel kind resonance. study this physics considering both two- three-dimensional excitonic materials embedded microcavity. highlight varied phenomenology those polaritons develop theoretical understanding their most peculiar features.