Pulse distortion in GaAs quantum wells studied by a light-gating technique.

Abstract

The pulse distortion in GaAs quantum wells was studied by means of a light-gating technique. In the experiment, we used the incoherent picosecond pulse to observe accurately the changes of the coherent spike and its surrounding envelope. The experimental results clearly showed that the pulse is not anomalously delayed but is strongly distorted around the exciton resonance. We also compared the results with a computational simulation based on the absorption saturation mechanism. The simulated results agreed well with experimental results. The simulation showed that the recovery time of the exciton saturation is 90 ps around the tail part of the exciton absorption. We also observed a reduction of the coherent spike around the exciton resonance. Theoretical calculations indicate that the coherent-propagation effect in the linear absorber causes the reduction of the coherent spike.