Diffraction behavior of polypyrrylarylenemethine/polyvinyl film to Gaussian beam

A new type of organic polymer nonlinear optical compound film known as polypyrrylarylenemethine/polyvinyl film was prepared. In the Z-scan experiment, two types of concentric diffraction rings were observed in the far field depending on the position of the sample relative to the Gaussian beam waist. This phenomenon can be explained by the diffraction effect of the Gaussian beam from the laser-induced phase-hole in the nonlinear medium caused by Kerr effect and thermo-optic effect. Based on Fresnel-Kirchhoff diffraction integral equation, a mathematical model on the diffraction of nonlinear optical media to Gaussian beam was established. The numerical calculating results are in good agreement with the experimental data.