Abstract

We have developed a technique for measuring the complete time-dependent intensity and phase of an arbitrary ultrashort laser pulse on a single-shot basis.¹ This technique, called Frequency-Resolved Optical Grating, or FROG, has been demonstrated in the ultraviolet, visible, near- and mid-infrared for pulses ranging from 10 fs to 2 ps in length. The FROG technique consists of generating an autocorrelation (either second- or third-order) of two replicas of the pulse in a nonlinear optical material, and then frequency resolving this autocorrelation signal.² This results in a data set known as a FROG trace, which is plotted as a function of frequency (wavelength) and time delay between the two réplicas of the pulse This experimentally generated FROG trace data is then used as input to a numerical algorithm that inverts the trace to find the complex electric field that generated the FROG trace.³ This algorithm is based on phase-retrieval techniques.

© 1995 IEEE