Theory of Gaussian beam Z scan with simultaneous third- and fifth-order nonlinear refraction based on a Gaussian decomposition method

摘要

We present a detailed theoretical investigation on the Gaussian beam Z scan for arbitrary aperture and arbitrary nonlinear refraction phase shifts, based on the Gaussian decomposition method, including cases when the medium exhibits the single (2n + 1)th-order nonlinear refraction effect and the simultaneous third- and fifth-order nonlinear refraction effects. We find the optimum sum upper limit, which is of great importance to fit the Z-scan traces and extract the nonlinear refraction coefficients related to the third- and fifth-order effects. This method has not only a high accuracy but is also time saving. We also discuss the influence of two-photon absorption on the Z-scan traces when materials possess the simultaneous third- and fifth-order nonlinear refraction effects associated with the two-photon absorption using the fast Fourier transform. (c) 2005 Optical Society of America