Two-color time-resolved Z-scan to study the thermal changes of the refractive index in liquids

Zscan technique is a powerful method to determine the sign and magnitude of the nonlinear refractive index of optical materials [1]. In this technique the sample is illuminated by a focused Gaussian beam. An aperture is placed between the sample and the detector, and the light transmitted through the aperture is monitored as the sample is moved along the propagation path of the beam through the focal region. The transmittance of another probe beam that is distorted with the refractive index changes caused by the illuminating beam, may be measured as well in the so called two-color extension of this technique [2,3]