Effect of particle size on nonlinear refractive index of Au nanoparticle in PVA solution

nonlinear refractive index of au nanoparticle suspended in pva solution was measured using a single beam z-scan technique. measurements were carried out using a green cw laser beam operated at 532 nm as excitation source. five nanoparticle samples with different particle sizes were prepa red by γ radiation method. the au nano-fluid shows a good third order nonlinear response for particle sizes ranging from 7.0 nm to 18.7 nm. the sign of the nonlinear refractive index was found to be negative and the magnitude was in the order of 10-8 cm2/w. the results show that the nonlinear effect tends to be increased linearly with the increasing of particle sizes thus could be a good candidate for nonlinear optical devices.