Large third-order optical nonlinearity of periodic gold nanoparticle arrays coated with ZnO

The third-order optical nonlinearity of a composite film consisting of periodic triangular gold nanoparticle arrays coated with ZnO was investigated by the z-scan technique. The third-order nonlinear susceptibility, χ⁽³⁾, measured at a wavelength of 532 nm with a pulse duration of 10 ns, was up to 1.3 × 10^-5 esu. The figure of merit, χ³/α (where α is the absorption coefficient) was about 1.1 × 10^-9 esu cm. The large optical nonlinearity is likely due to the strong local electromagnetic field near the triangular gold particles and ZnO matrix. The results show that the composite film has great potential for nonlinear optical devices.