Third Order Optical Nonlinearity of Silver Nanoparticles Prepared by Chemical Reduction Method

In this study, silver colloidal nanoparticles have been prepared by chemical reduction of silver nitrate by trisodium citrate as a reduction agent. The adding time of the reduction agent was held constant while the time of stirring was varied. The resulting silver nanoparticles were characterized by UV-VIS absorption spectroscopy. The non-linear refractive index and absorption coefficient of silver nanoparticles were investigated using a single beam z-scan technique. The excitation source was a continuous wave (CW) of 532 nm diode laser with a beam power of 40 mW. All investigated samples showed negative and large thermally-induced non-linear refractive indices. Other nonlinear optical parameters (i.e.β,χ_r^((3)),χ_i^((3))) were also calculated. Our measurements confirm that the non-linear parameters are caused by self-defocusing process making them potential candidates for nonlinear optical devices.