Phase defects in self-focusing of ultrashort pulses

We report the numerical observation of edge-type phase defects which occur during the self-focusing of ultrashort pulses. We identified two distinct k inds of defects, farmed at the temporal or spatial edges of the pulse. We s how the effect of phase defect creation on the dynamics and the eventual ar rest of the self-focusing process. Phase defects often lead to the inversio n of the phase fronts curvature, transforming contracting pulses into expan ding pulses.