Nonlinear optical properties of gold nanoparticles produced by laser ablation at two different radiation wavelengths

Abstract

In this study, gold nanoparticles were synthesized by laser ablation of Au bulk in distilled water. The laser used is Nd: YAG laser, which has a fundamental harmonic wavelength (λ=1064nm) and second harmonic wavelength (λ=532nm). In order to control the size of Au nanoparticles (NPs), we used sodium citrate as a stabilizer. Morphology, structure and linear optical properties of Au NPs samples were characterized by transmission electron microscopy (TEM observation), XRD diffraction (XRD) and UV–Visible spectroscopy. Furthermore, the chemical structure in solution of Au NPs was studied by Fourier transform-infrared spectroscopy (FTIR). The nonlinear optical parameters of these Au NPs were studied using the Z-scan method. We found the optimal values of fluencies and laser pulse repetition rates to achieve the smallest size values and the most distribution of the produced gold nanoparticles. It is resulted that due to the very small size of NPs, the nonlinear optical parameters show larger values. It is 107 order of magnitude larger than what has been reported for the nonlinear refractive index in previous researches. In addition, gold nanoparticles that are produced with a laser wavelength of 1064 nm and have a high nonlinear refractive index can be used in chip-based sensors. Finally, the use of these Au NPs in optical switching devices was investigated by the two figures of merit method, which indicated that these Au NPs are practical tools for optical switching devices.