Discrimination between two distinct nonlinear effects by polarization-resolved Z-scan measurements.

We investigated how the Z-scan technique can be explored to distinguish two types of nonlinear refractive effects by employing two distinct laser polarizations. It is possible that pure electronic, molecular orientation and thermal nonlinear effects may occur simultaneously during light-matter interaction. We found a way to discriminate and quantify two distinct nonlinear processes from Z-scan signals measured with linear and circular polarizations.

Measurement of third-order nonlinearities in selected solvents as a function of the pulse width.

We investigated the magnitude and origin of the nonlinear refraction in several solvents with the nonlinear ellipse rotation measurements as a function of the pulse duration in the range from 60fs to 2ps. Due to the presence of non-instantaneous nuclear contributions concurrently with the nearly instantaneous electronic nonlinearity, solvents present effective refractive nonlinearities that depend on the pulse duration. By proposing an empirical model where the nonlinearity grows exponentially with the pulse duration normalized to the response time, we could separate contributions from fast isotropic and slow nuclear reorientational nonlinearities.