Third-order optical nonlinearities of Ag nanoparticles fabricated by two-step ion exchange in glass

We present third-order optical nonlinearities of Ag nanoparticles fabricated using a two-step ion exchange method. The nonlinearities are studied using the well-known Z-scan technique. In our experiments, we use a Ti-Sapphire laser source operating at 800 nm, which is far from the resonance of the Ag nanoparticles. The nonlinear refraction of these nanoparticles is studied using the closed aperture configuration of the Z-scan method. Contrary to expectations from previous studies for similar-sized nanoparticles, our nanoparticles possess positive nonlinear refractive index. The estimated nonlinear refractive indices are in the range of 10 -12 cm 2 /W.