PHASE COHERENCE OF 2D EXCITONS IN GaAs-AlGaAs QUANTUM WELLS

We have studied photon echoes on a picosecond timescale from 2D excitons in GaAs-AlGaAs quantum wells. A theoretical model is used which considers phase relaxation during excitation. We find considerable deviations from the usual photon echo behavior for pulse lengths comparable to the phase coherence time. Line shape analyses of our experimental data yield the phase coherence times which are found to vary strongly across the inhomogeneously broadened exciton line.