Photon echoes from two-dimensional excitons in GaAs-AlGaAs quantum wells

Abstract

We report photon echoes from two-dimensional (2D) excitons in a GaAs-AlGaAs quantum well structure at 2 K. We analyze our data with a theoretical model of the generation of photon echoes by pulses of finite length which includes phase relaxation during excitation. A line shape analysis yields the phase relaxation time of 2D excitons. We find that the phase coherence near the line center decays, together with the resonant population, within 4 ps, whereas well below line center the phase coherence is conserved for times up to 20 ps.