Measuring spatio-temporal pulse distortions using GRENOULLE

Abstract

We show that GRENOUILLE, the experimentally simple version of frequency-resolved optical gating (FROG) can measure the two spatio-temporal distortions, namely spatial chirp and pulse-front tilt, in addition to the pulse intensity and phase. This is done without a single alteration in the experimental setup. Specifically, pulse-front tilt yields a displacement of the otherwise centered trace along the delay axis while spatial chirp causes a shear to the otherwise symmetrical GRENOUILLE trace. We develop a more general FROG pulse-retrieval algorithm based on the Levenberg-Marquardt algorithm, which can retrieve not only the pulse intensity and phase but also both the spatial chirp and pulse-front tilt from GRENOUILLE traces. Lastly, we also show that, by employing the exotic nonlinear crystal Proustite, GRENOUILLE can be extended to measure fiber-laser pulses with wavelengths near 1.5μm. The high nonlinearity of Proustite compensates for the lower output power of fiber lasers. Also Proustite has so high dispersion that it can spectrally resolve these relatively narrowband pulses. We experimentally test all of these innovations and obtain perfect agreement with the expected results.