Study of the nonlinear optical properties of platinum and gold nanoparticles

This work presents a study on the thermo-optical properties of colloidal gold nanoparticles (AuNPs) and platinum nanoparticles (PtNPs) under a low power laser irradiation at 532 nm. Samples of gold and platinum were synthesized by nanosecond pulsed laser ablation of pure gold and platinum plates in the distilled water. The formation of the AuNPs and PtNPs was evidenced by optical absorption spectra and transmission electron microscopy. The thermo-optical properties of AuNPs and PtNPs were studied using Z-scan technique. The nonlinear optical measurments exhibited a very large nonlinear refraction close to the surface plasmon resonance frequency of the nanoparticles. Our results revealed that the diffusion in the colloids is due to nonlocal thermal process. This work suggests that thermal nonlinear refraction will play an important role in development of photonic application involving metal nanoparticles colloids.