الفهرس 
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Abstract
This thesis presents an experimental investigation using Z-scan technique on the dependence of the nonlinear optical (NLO) properties of silver nanoparticles (AgNPs) on the excitation wavelength and the AgNPs concentration and size. Using a 532 nm Nd: YAG laser beam at a fixed pulse energy of 100 mJ/pulse for different ablation times of 5, 10, 15 min, AgNPs were produced on a silver target that was immersed in distilled water. The optical characteristics and concentrations of laser-produced AgNPs are examined using UV-Vis spectroscopy and an atomic absorption spectrometer. Utilization of a transmission electron microscope (TEM) to gauge the dimensions of AgNPs. The consequences of the TEM research demonstrated that the spherical AgNPs produced by the laser are slightly smaller as the laser ablation time is increased. During ablation times of 5, 10, and 15 min, the average AgNP sizes were 13.2, 13 and 12 nm, resp. As AgNP size rises, the bandgap expands, according to UV-Vis spectroscopy. Furthermore nonlinear optical properties of these AgNP colloids are then examined using the open aperture (OA) and closed aperture (CA) Z-scan techniques, which have a fixed excitation power of 1W and variable excitation wavelengths ranging from 740 to 820 nm. The AgNP colloids investigated at different concentrations and sizes. The nonlinear absorption coefficient (α3) and nonlinear refractive index (n2) are measured. The results show that both n2 and α3 increase as the concentration of AgNPs rises due to the influence of the average size. n2 and α3 DROP as the AgNPs’ average size and excitation wavelength rise. At a concentration of 3.35 mg/L of AgNPs, the maximum values of α3 and n2 are 5×10-20 cm3/W2 and 4.055×10-15 cm2/W, respectively, at an excitation wavelength of 740 nm. In moreover, independent of the ablation duration, the AgNPs colloids exhibit reversed saturable absorption (RSA) (positive nonlinear absorption) and a negative nonlinear refractive index n2.