Polaritons in superlattices and in microcavities.

A description of polariton effects on excitons in multiple quantum wells (MQWs), superlattices (SLs), and semiconductor microcavities is presented. The non-local semi-classical theory in a transfer matrix formulation is adopted. The radiative width in MQWs at k = 0 increases first with the number of wells N, then goes to zero as N --> infinity, where stationary SL polaritons are recovered. The crossover from weak- to strong-coupling regimes for QW excitons in microcavities is described. The complex energies of the mixed exciton-radiation modes are shown to be measurable by time-resolved transmission experiments.