A Novel Technique to Measure the Spatial–Temporal Intensity of an Ultrashort Pulse

Abstract

Based on a modified cross-correlation technique, we experimentally demonstrate a technique for measuring the spatial–temporal intensity of laser pulses. Pulse widths at different spatial positions of the ultrashort pulse are measured by changing the scan position of the probe beam. Due to the existence of residual chirp in the transverse position, pulse widths at the center of the beam are less than that at the edge. By measuring the temporal evolution in the fastest growth area of spatial intensity during small-scale self-focusing, we find that its pulse width decreases as power increases because of the spatial–temporal coupling effect. The results show that this method not only can be used to accurately measure the pulse width at any one spatial position of the beam, but can also be useful for real-time monitoring of the spatial–temporal evolution.