@article{Jaffar_2020, title={The Effects of Initial Laser Intensity on the Nonlinear Optical Properties of The Laser Dye DQOCI Doped Films Using Z-Scan Technique}, volume={61}, url={https://ijs.uobaghdad.edu.iq/index.php/eijs/article/view/1706}, DOI={10.24996/ijs.2020.61.10.11}, abstractNote={<p>This study is dedicated to investigate the effects of initial laser intensity on the nonlinear optical properties of the laser dye DQOCI dissolved in methanol with a concentration of 10 <sup>-5 </sup>M and doped with PMMA film. The properties were studied by using open and closed aperture Z-scan technique, with different levels of initial intensity (I<sub>0</sub>), excited by continuous diode solid-state laser at a wavelength of 532 nm. Three lenses of different focal lengths were employed to change the radius of the Gaussian laser beam and then change the initial intensity. For I<sub>0</sub>= 6.83 and 27.304 kWatt/cm<sup>2</sup>, the Z-scan curves show a saturation of absorption (SA) known as the negative type of nonlinearity, in which the absorption coefficient Î² <sub>2</sub> decreases and the transmittance increases with increasing the initial laser intensity. With I<sub>0</sub> equal to 3.03 KWatt/cm<sup>2</sup>, the nonlinear absorption changes from SA to RSA, where the transmittances is reduced with the increase of intensity (zï€½0) as analyzed by the theory of free carrier nonlinearities. The closed aperture z-scan shows a pre-focal transmittance minimum (valley) and a post focal transmittance maximum (peak) which reflects the z-scan signature of a positive nonlinearity (self-focusing) due to Kerr effect. Each of nonlinear refractive index (n<sub>2</sub>), nonlinear absorption coefficient (Î² <sub>2</sub>), and third-order nonlinear optical susceptibility (Ï‡<sup>3</sup>) are intensity-dependent.</p>}, number={10}, journal={Iraqi Journal of Science}, author={Jaffar, Amal F.}, year={2020}, month={Oct.}, pages={2551-2561} }