Measurement of transient nonlinear refractive index in gases using xenon supercontinuum single-shot spectral interferometry

A highly stable version of spectral interferometry is demonstrated, allowing single shot measurement of ultrafast high field processes using modest energy lasers, with pump and probe pulses totaling less than 1 mJ. The technique makes possible reconstruction of ultrafast refractive index transients with one-dimensional spatial resolution, limited only by the bandwidth of the supercontinuum pulse (~100 nm) and instrument resolution. The ultrafast nonlinear Kerr effect in glass, and in Ar, N(2), and N(2)O gases is measured, along with plasma generation in Ar. The inertial contribution to the nonlinear index from N(2) and N(2)O molecular rotation is also observed.