Everything you've always wanted to know about an ultrashort pulse but thought was immeasurable

Abstract

We describe two techniques for measuring the complete spatio-temporal intensity and phase, <i>E(x,y,z,t)</i>, of an ultrashort pulse. The first technique is an experimentally simple and high-spectral resolution version of spectral interferometry, which uses fiber optics to introduce the pulse that is to be characterized into the device. By scanning the fiber around the focus, this device can be used to measure the spatio-temporal field of a focusing ultrashort pulse. We illustrate this technique by measuring the spatio-temporal filed for several different focused pulses. The other technique measures the complete spatio-temporal field of a pulse using a very simple experimental setup. While this technique will not work at the focus, it is single shot and requires only a single camera frame to reconstruct the complete filed versus space and time. This technique involves measuring multiple holograms, each at a different wavelength, and all in a single camera frame. To test this technique we show that it can accurately measure the spectral phase. We also illustrate this technique by measuring, <i>E(x,y,t)</i> of a single laser pulse.