الفهرس 
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Abstract
Nonlinear optics is well recognized as a powerful tool for studying the nonlinear optical properties of molecules, nanostructures, and materials. In this master thesis, the nonlinear optical properties of AgNPs colloids in distilled water, when irradiated with 100 fs laser pulses, were investigated experimentally using the Z-scan technique. At a constant wavelength of 760 nm and different excitation powers ranging from 0.7 to 1.5 W, the nonlinear absorption coefficient and nonlinear refractive index were measured. For all samples, AgNPs colloids exhibited reverse saturable absorption (positive nonlinear absorption) and self- defocusing (negative nonlinear refractive index). It has been founded that the size of noble metal nanoparticles have a significant impact on their nonlinear optical properties. The thermal lens effect was handled with a new approach to account for accumulative thermal lensing in the sample caused by high repetition rate fs laser pulses. The AgNPs colloids are synthesized by laser ablation of silver bulk in distilled water using a 532 nm Nd: YAG laser with different ablation energies fluence of 9, 15.5, and 26 ⨯104 (J/cm2) over a 30 min ablation time. The nanoparticle size, shape, and absorption spectra of nanoparticle colloids were determined using transmission electron microscopy and an ultraviolet-visible spectrophotometer. Spherical AgNPs are formed with an average diameter ranging from 7.5 to 12 nm. As the laser ablation energy fluence increases, the average size of the AgNPs decreases while the bandgap energy increases. As the excitation laser power and AgNPs size increase, the nonlinear absorption coefficient and nonlinear refractive index decrease. The optical limiting behavior of the AgNPs colloids at different ablation energies fluence is studied by using a Z-scan experimental setup. The optical limiting performance of AgNPs improves with increasing laser ablation energy fluence, with the best performance at 26⨯104 (J/cm2).