Quantification of phase instabilities in amplitude swing for ultrashort pulse train characterization

These dynamics can often be extracted from a two-dimensional trace consisting of a set of nonlinear spectra, using an iterative algorithm. Typically, the measurement of this trace requires integrating the signal of many pulses, which implies that the trace does not correspond to a single pulse when shot-to-shot variations occur.

In this case, the pulse train can be characterized by a base pulse and a metric that quantifies its instabilities. Here, we demonstrate that the amplitude swing technique is highly sensitive to pulse-train instabilities, allowing not only for their detection but, crucially, for their quantification. First, we examine the analytical components of the amplitude swing trace.