The influence of the pulse width on the nonlinear refractive index of organic solvents

There are materials which their nonlinear refractive index (n2) have contributions from fast isotropic and slow reorientational effects. Due to the presence of the slow noninstantaneous effect, the magnitude of the effective nonlinear refractive index (n2, eff) depends of the pulse width (τ). Here, we propose to measured the n2eff of several organic solvents as a function of pulse width and from these data extract information about the fast and the slow nonlinearities, including magnitudes and response times (τ0). We have used an accurate and single beam nonlinear ellipse rotation (NER) measurement to measure the third-order nonlinear susceptibility, B=6x1221 [1, 2], which is proportional to n2. The NER signal is a nonlinear refractive effect, which is observed when an intense elliptical polarized beam propagates through a medium.