Z-Scan measurements of optical nonlinearities for (3GO) dye

In this paper a sensitive single-beam technique for measuring both the nonlinear refractive index and nonlinear absorption coefficient for 3GO dye were reported. Descriptions for the experimental details and theoretical analysis including cases where nonlinear refraction is accompanied by nonlinear absorption were presented. In these experiments, the transmittance of a sample is measured through a finite aperture in the far field as the sample is moved along the propagation path (Z) of a focused Gaussian beam. The sign and magnitude of the nonlinear refraction are easily deduced from such a transmittance curve (Z-scan). Employing this technique, the nonlinear refraction is accompanied by nonlinear absorption, it is possible to separately evaluate the nonlinear refraction as well as the nonlinear absorption by performing a second Z scan with the aperture removed. We demonstrated this method for (3GO) dye at 532 nm where two-photon absorption is present and n2 is positive. Also the optical proprieties (absorption, fluorescence spectra and the quantum efficiency) of 3GO dye solution in chloroform with different concentrations were evaluated.