Large optical nonlinearity of Au nanoparticle-dispersed Ba _0.6Sr_0.4TiO₃ films prepared by pulsed laser deposition

Crystallized Au nanoparticle-dispersed Ba_0.6Sr _0.4TiO₃ (Au : BST) thin films were prepared on MgO (1 0 0) substrates by pulsed laser deposition. The peak of the linear absorption coefficient for the film shifts to longer wavelength with an increase in Au concentration. Among all the tested samples, the largest values of third-order nonlinear susceptibility were calculated to be -1.93 × 10^-6 esu and 1.13 × 10^-5 esu corresponding to imaginary and real parts, respectively, which were determined by a single beam Z-scan at a wavelength of 532 nm with a laser duration of 10 ns. The relationship between Au concentration and third-order nonlinear susceptibility was also analysed.