Effects of the morphology and nanostructure on the optical nonlinearities of Au:BaTiO3 nanocomposite films

Metal nanocomposite thin films formed by nanometer-sized gold particles embedded in BaTiO3 matrices (Au:BaTiO3) were fabricated on MgO (100) and glass substrates using a pulsed-laser deposition technique. The high-resolution transmission electron microscopy analysis indicated that the morphology of gold particles and the structure of BaTiO3 matrices changed remarkably with the change of the substrate temperatures. Crystal lattice fringes from the Au nanocrystals and BaTiO3 matrices were clearly observed. The nonlinear optical properties of the Au:BaTiO3 nanocomposite films were measured using the Z-scan method at the wavelength of 532 nm. A sign reversal was demonstrated in the nonlinear absorption coefficient (β) and the nonlinear refractive index (n2) of Au:BaTiO3 films with the same Au concentration but a different nanostructure.