Experimental Z-scan Measurements Using Gaussian-Bessel Beams

Abstract

Z-scan technique is a simple and widely used experimental method to measure the nonlinear refractive index of optical materials. Typically a longitudinal scan of the sample to test around the waist of a Gaussian beam is performed and the transmitted optical power is measured, in far field condition through a small aperture by a photodiode, as function of the position. Several modifications to the Z-scan technique have been proposed to increase its sensitivity [1-3]. One of these papers suggests theoretically the gradual transformation of the Gaussian beam to Bessel-Gauss beam [3] to increase the sensitivity by a factor of 40. In this work we present experimental results of Z-scan measurements using a focused Gaussian beam from a cw He-Ne in combination with an axicon to obtain a Bessel-Gauss beam to implement the z-scan technique. The results obtained show an increasing in the amplitude of the curve when is compared with the conventional Z-scan results for this type of samples.