Z-Scan: A Simple And Sensitive Technique For Nonlinear Refraction Measurements

Abstract

We describe a sensitive technique for measuring nonlinear refraction in a variety of materials that offers simplicity, sensitivity and speed. The transmittance of a sample is measured through a finite aperture in the <i>far-field</i> as the sample is moved along the propagation path (z) of a focused Gaussian beam. The sign and magnitude of the nonlinearity is easily deduced from such a transmittance curve (Z-scan). Employing this technique a sensitivity of better than &lambda;/300 wavefront distortion is achieved in n₂ measurements of BaF₂ using picosecond frequency doubled Nd:YAG laser pulses.