Abstract

We report studies of exciton dephasing in quantum dot (QD)-like islands in narrow GaAs quantum wells (QWs). Using three- pulse transient four-wave mixing (FWM), we compare dephasing rates directly with population decay rates. This comparison reveals a pure dephasing process that dominates excitonic dephasing at elevated temperatures but does not involve exciton population relaxation. The pure dephasing process arises from a mixing of excitonic states with a continuum of acoustic phonons and is enhanced by three-dimensional quantum confinement. The magnitude as well as the temperature dependence of the pure dephasing rate is well described by a theoretical model that generalizes the Huang-Rhys theory of F centers to include off-diagonal exciton-phonon coupling. These studies have led to a fundamental understanding of dephasing in QDs.¹

© 1998 Optical Society of America