On the nature and dynamics of low-energy cavity polaritons
  Low-energy polaritons in semiconductor microcavities are important for many processes such as, e.g., polariton condensation. Organic microcavities frequently feature both strong exciton-photon coupling and substantial scattering in the exciton subsystem. Low-energy polaritons possessing small or vanishing group velocities are especially susceptible to the effects of such scattering that can render them strongly localized. We compare the time evolution of low-energy wave packets in perfect microcavities and in a model 1$d$ cavity with diagonal disorder to illustrate this localization of polaritons and to draw attention to the need to explore its consequences for the kinetics and collective properties of polaritons. 
V.M. Agranovich, Yu.N. Gartstein