Frequency-resolved optical gating of highly chirped ultrabroadband pulses

Abstract: This article describes a simplified reconstruction algorithm for frequency resolved optical gating (FROG) measurements of highly (monotonically) chirped pulses. The FROG traces are calculated using the stationary phase approximation, significantly reducing the data size and convergence time compared to discrete Fourier transform based methods. The method is verified via second harmonic generation FROG simulations and measurements of pulses centred at 800nm with a bandwidth of 55nm stretched to 32ps at the 1% intensity level, corresponding to a time-bandwidth product of 830.