Coherent interactions in pump-probe absorption measurements: The effect of phase gratings

We show that in order to describe completely the coherent coupling between the pump and probe pulses in a pumpprobe measurement of transient absorption, the influence of induced phase gratings must be included. The importance of phase gratings is demonstrated experimentally for the case of a bleachable dye and analyzed in terms of transient four-wave mixing. These results are relevant to the interpretation of pump-probe measurements on all time scales performed with pulses from a single laser, particularly when the pulse duration is comparable with the material response time. © 1985 Optical Society of America.