Sensitivity enhancement for measurement of nonlinear refraction using top-hat beams

Abstract

A simple and high-sensitivity technique is presented to investigate nonlinear refraction. In this technique, a combination of aperture and obscuration disk is introduced in the measurement system. Compared to the top-hat Z-scan, the curves of modified top-hat Z-scan for the nonlinear refraction show a single peak. Furthermore, the sensitivity of this new technique can be more than two orders of magnitude enhanced. Nonlinear refraction of Nd-doped phosphate glass is investigated using this technique with 19 ps pulses at wavelength of 532 nm.