We use both a Fourier-transform-based analysis and time-retrieval
calculations to get time-resolved measurements of the reflectivity
and the phase shift of a chirped probe pulse interacting
with a fs-laser-produced plasma by spectral interferometry
in a single shot. We have devised a novel dual-quadrature
Mach–Zehnder configuration in which wavefront division
is used to obtain spatial fringes from the perturbed and
unperturbed probe simultaneously. We demonstrate the capability
of this technique with fully analyzed experimental data on the
interaction of a femtosecond laser with C3H6
and C samples, showing 35-fs time resolution.