Improvement of Mach–Zehnder interferometry technique for third-order susceptibility measurement

Abstract

We present in this paper an improved method to measure the third-order nonlinearity of poor optical quality samples. The principle is based on a pump/probe experiment using a Mach–Zehnder interferometer coupled to a CCD camera. The method first consists of recording the interference pattern in absence of pump beam thus allowing to characterize the linear properties of the sample. This acquisition is then compared to the interference pattern when the pump beam generates a nonlinear dephasing. From these data we can extract the nonlinear index coefficient. Therefore poor optical quality samples can be characterized because either inhomogeneities or surface defects induce linear amplitude or phase variations.