Experimental measurement of ultrashort pulse evolution at different spatial positions in nonlinear media

• The temporal evolution of ultrashort pulses before beam splitting.
• Different spatial positions have different modulation growths.
• Partial spatial intensity changes impact on temporal evolution.

The temporal evolution of ultrashort pulses before the beam splitting is very useful for filamentation theory. In this article, we experimentally demonstrated the temporal evolution of ultrashort pulses in the different spatial positions during small-scale self-focusing. The simulation results are found to be in good agreement with experiment measurements.