Spectral diffusion within exciton line in GaSe

Abstract

The spectral diffusion across the exciton line in GaSe is observed in two types of four-wave-mixing experiments. In the stimulated photon echo experiment, the signal shows a non-exponential decay as the waiting time between the second and third pulses increases. This behavior begins clearly from a few 10 ps of the waiting time. The deformation of the signal profile depending on the delay time of first two pulses is also observed in the transient grating-type signal. These results are in good agreement with the result of a theoretical calculation based on a stochastic model.