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

• The nonlinear-imaging technique is used to examine the nonlinearity of thick sample.
• The effective interaction lengths are obtained by plotting the relation of ΔTΔT with L.
• The effective interaction lengths can be used to fit the experimental data. It shows reasonable results for thick CS2 by using this one-single-shot method.

The third-order nonlinear refractive index of carbon disulfide (CS2) 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 n2 of CS2 can be determined, which suggests a one-single-shot method for the investigation of optical nonlinearity in thick medium.