Nonlinear Optical Properties of Gold-silica Nano-particles

A gold/silica nanocomposite was prepared via a laser ablation method and was characterized via UV-visible (Vis) absorption spectrometry and field emission scanning electron microscopy (FESEM). The Au@SiO2 nano composite was formed via nanosecond-pulsed laser irradiation on a gold plate in a silicon nanoparticle (NP) colloidal solution, which had been prepared through the laser ablation of Si wafer in deionized water and polyvinylpyrrolidone surrounding liquids; whereas the SiO2@Au nanocomposite was formed by ablating silicon wafer from a colloidal solution of gold NPs. The UV-Vis absorption spectrum of the core-shell colloidal solutions showed a surface plasmon resonance peak at 524 nm. The diameter of the core part and the shell thickness of both NPs in the solution were confirmed by FESEM images. The nonlinear optical (NLO) properties of both colloidal solutions were studied using the Z-scan method. Results showed considerable improvement for NLO properties by replacing water with polyvinyl lpyrrolid one as surrounding liquids. The nonlinear absorption value was improved by one order of magnitude with a negative sign, which illustrated a storable absorption phenomenon.