  Single-shot supercontinuum spectral interferometry (SSSI) is an optical
technique that can measure ultrafast transients in the complex index of
refraction. This method uses chirped supercontinuum reference/probe pulses that
need to be pre-characterized prior to use. Conventionally, the spectral phase
(or chirp) of those pulses can be determined from a series of phase or spectral
measurements taken at various time delays with respect to a pump-induced
modulation. Here we propose a novel method to simplify this process and
characterize reference/probe pulses up to the third order dispersion from a
minimum of 2 snapshots taken at different pump-probe delays. Alternatively,
without any pre-characterization, our method can retrieve both unperturbed and
perturbed reference/probe phases, including the pump-induced modulation, from 2
time-delayed snapshots. From numerical simulations, we show that our retrieval
algorithm is robust and can achieve high accuracy even with 2 snapshots.
Without any apparatus modification, our method can be easily applied to any
experiment that uses SSSI.
