Impact of wave-envelope dynamics on beam and pulse break up in X/sup (2)/ media

The purpose of this work is to show how the evolution of the input wave-envelope profile in phase matched second-harmonic generation is able to force a pure spatial or a pure temporal break-up, depending on the relative weight of diffraction versus group velocity dispersion. In order to clarify the underlying dynamics this study presents the results of 2+1 D numerical simulations (1 spatial, 1 temporal + 1 propagation dimensions). The plots give the spatio-temporal intensity map of the fundamental-wave, at different propagation lengths inside the crystal.