Femtosecond dynamics of excitons in quantum wells and quantum well microcavities

Investigations of femtosecond dynamics of excitons in two different regimes are reported: 1. perturbative or weak coupling regime where the exciton decay is irreversible (i.e. excitons in quantum wells), and 2. non‐perturbative or strong coupling regime (i.e. quantum well excitons in microcavities) where the coherent exchange of energy between the coupled cavity and exciton modes dominates the femtosecond dynamics. In the perturbative regime, the first femtosecond luminescence measurements are reported, which show (i) a finite rise time for the emission from resonantly‐excited excitons and (ii) femtosecond quantum beats of heavy‐hole and light‐hole excitons. In microcavities, the first nonlinear measurements are reported, which show quantum beats from the coupled cavity‐exciton modes, and provide information about the system not available from linear measurements.