Coherent Manipulation of the Exciton Orientation in Quantum‐Wells

We demonstrate that the optical orientation of excitons can be coherently controlled and directly observed in a resonant time-resolved photoluminescence experiment. The optical dephasing time of excitons, their longitudinal and transverse spin relaxation times, and their radiative lifetime, are measured with strictly the same experimental conditions. This technique, which relies on the linear response of the crystal, is used to investigate the spin-dependent exciton–exciton interactions.