Effect of sample position on formation of spatial-self phase modulation ring patterns in poly(azaneylylidene-acylene)

Poly(azaneylylidene-acylene) "DAZA" polymer has been synthesized and characterized using different spectroscopic techniques. Self-diffraction ring patterns at far field were observed, when the DAZA polymer was irradiated with a CW laser beam. The influence of sample position, geometrical pumping and laser power has been investigated on the formation of the far field self-diffraction ring patterns of the Gaussian laser beam passing through the DAZA polymer as nonlinear medium. Then, the Fresnel-Kirchhoff diffraction formula was applied to perform simulation of the self-diffraction ring patterns with different laser power at two sample positions before and after the focal point (z = 0) with respect to the geometrical pumping. Our results have shown the effect of type of geometrically pumping on the sample cell (horizontally /vertically) with respect to the distortion of the SSPM patterns. It has been found that, good consistent agreements between experimental and theoretical patterns.