Excitonic wave packets observed in space- and time-resolved pump and probeexperiments

We investigate the coherent time regime in space- and time-resolved pump an d probe experiments on a symmetrically strained InGaAs/GaAsP multiple quant um well. The spatial width of the transmission profiles shows a modulation which reflects the dynamics of an excitonic wave packet. This spatio-tempor al beating originates from the combined action of various signal components which are detected simultaneously because of the collinearity of our exper iment. The experimental results are in qualitative agreement with calculati ons obtained with a simplified model on the Hartree-Fock level. (C) 1999 El sevier Science Ltd. All rights reserved.