  Strongly coupled organic systems are characterized by unusually large Rabi
splittings, even in the vacuum state. They show the counter-intuitive feature
of a lifetime of the lower polariton state longer than for all other excited
states. Here we build up a new theoretical framework to understand the dynamics
of such coupled system. In particular, we show that the non-Markovian character
of the relaxation of the dressed organic system explains the long lifetime of
the lower polariton state.
