Toward single-shot measurement of a broadband ultrafast continuum

We discuss the problem of measuring the intensity and phase of a broadband continuum in a single shot, considering three possible methods, and perform preliminary measurements using one of them. Our measurements use transient-grating cross-correlation frequency-resolved optical gating (TG XFROG) with a third-order nonlinear medium, which currently can phase match over 300 nm simultaneously. We demonstrate this technique for a continuum generated in bulk fused silica that is 12.5 mm thick. Due to limited reference-pulse energy, we do not achieve a true single-shot measurement, instead averaging over approximately five shots. The retrieved trace and spectrum contain fine structure, and the retrieved temporal phase is mainly quadratic.