Intensity-dependent temporal laser pulse shaping and propagation in ZnSe

The shape of a 40-ps 1064-nm laser pulse propagating through ZnSe at different intensities was investigated using a single-shot optical Kerr gate. At high intensity similar to3.65 GW/cm(2) the pulse peak moves forward in time by about 15 ps from the position at low intensity and the full width at half maximum reduces from 40 to 27 ps. This pulse advancement and time shortening are attributed to a combination of two-step absorption and negative nonlinear dispersion. The numerically simulated results based on these two processes are in good agreement with the experimental results. (C) 2002 Published by Elsevier Science B.V.