Nonlinear optical parameters of colloidal silver at various stages of aggregation

The Z-scan method is used to study the variation in the nonlinear susceptibility χ⁽³⁾ (−gw; ω, ω, −ω) and nonlinear refractive index of colloidal silver with the degree of aggregation under the action of picosecond and nanosecond radiation (λ=1064 nm). The values of χ⁽³⁾ for aggregated silver that are defined by Kerr nonlinearity and thermal self-focusing are found to be −1.5×10⁻¹⁴ and −4.4×10⁻¹¹ esu, respectively. The time evolution of the picosecond pulses passing through the colloid is investigated.