Measurement of nonlinear refraction of thick samples using nonlinear-imaging technique with a phase object

Abstract The third-order nonlinear refractive index of carbon disulfide (CS 2 ) with different thicknesses is measured by a nonlinear-imaging technique with a phase object (NIT-PO). The propagating characteristics of the laser beam within thick medium are analyzed by numerically solving the electromagnetic wave equation. By theoretically calculating, we study the relationship of the phase shift induced by nonlinear refraction versus medium thicknesses. Fitting the output image with the help of the effective interaction length, the nonlinear refractive index n 2 of CS 2 can be determined, which suggests a one-single-shot method for the investigation of optical nonlinearity in thick medium.