Sensitivity-enhanced Top-hat Z-scan By Absorbing Part Of The Incident Light

With the development of the research of nonlinear optics, nonlinear optical measurement technology has been more and more important. The Z-scan technology is widely used because of it has a lot of advantages such as single laser beam, high sensitivity, nonlinear refractive index and nonlinear absorption coefficient can be measured at the same time. Many alterative or improved Z-scan techniques have been developed since the original Z-scan technology was first proposed and these methods have greatly enhanced the measurement sensitivity and expanded the range of the applications of Z-scan technology.This paper introduces several improved high-sensitivity Z-scan techniques compared with the original Z-scan,and we propose a new Z-scan technology based on the top-hat beam Z-scan which own higher sensitivity and easy to operated. This modification involves placing a gilded glass plate at the entry of the traditional top-hat beam Z-scan that absorbs part of the beam. The sensitivity of measurement is greatly enhanced with this method compared with the original top-hat beam Z-scan method. First we conduct the theoretical analysis and numerical simulation of our improved ps(picosecond) top-hat beam Z-scan. The results of theoretical simulation show that our method has a larger sensitivity than the original top-hat beam Z-scan, and the sensitivity is related with transmittance and diameter of the absorption film. So we can choose proper parameters of the film to get the best sensitivity. In order to verify the feasibility of our improved method, we use CS2 as the standard sample to conduct Z-scan experiments. The results of the experiments are consistent with the simulation results.