Size-dependent enhancement of nonlinear optical properties in nanocolloids of ZnO

We have investigated the third-order nonlinearity in ZnO nanocolloids with particle sizes in the range 6–18 nm by the z-scan technique. The third-order optical susceptibility χ(3) increases with increasing particle size (R) within the range of our investigations. In the weak confinement regime, an R2 dependence of χ(3) is obtained for ZnO nanocolloids. The optical limiting response is also studied against particle size.