Nonlinear optical properties of dielectric nanocolloids: Particle size and concentration effects

The nonlinear optical properties of different samples of dielectric nanocolloids and their application to generate optical spatial solitons in two transverse dimensions are investigated. Each sample is constituted by a suspension of polystyrene nanospheres in water, and we analyze four cases with two different particle sizes (62 nm and 77 nm in diameter) and concentrations (0.5% and 1.0% solids). The z-scan technique is used to evaluate and compare the nonlinear refractive index of the nanocolloids. A detailed experimental study on the formation of soliton-like beams as a function of different parameters is also presented. Importantly, the generated solitons propagate along distances exceeding by one order of magnitude the propagation distances observed previously in the same kind of media.