PHASE-DEPENDENT HARMONIC EMISSION WITH ULTRASHORT LASER-PULSES

We consider harmonic generation by atoms exposed to an intense laser p ulse of a few femtoseconds. Our results, obtained by solving numerical ly the corresponding three-dimensional time-dependent Schrodinger equa tion, demonstrate the strong sensitivity of the harmonic spectra to th e phase of the laser. These results are explained in terms of both qua ntum and classical dynamics. We show that this phase sensitivity may b e exploited in order to probe the laser phase for ultrashort pulses. O ur discussion about this new method of diagnosis takes into account pr opagation effects.