Resonant absorption quenching and enhancement of optical nonlinearity in Au:BaTiO3 composite films by adding Fe nanoclusters

We present an approach to enhance the figure of merit χ(3)/α (with χ(3) being the third-order nonlinear susceptibility and α the optical absorption coefficient) in metal-dielectric composites. Nanocomposite thin films containing metal nanoclusters were obtained by embedding gold, or gold+iron in BaTiO3 matrices using the pulsed laser deposition technique. In the optical absorption spectra, the Au:BaTiO3 films showed a strong absorption peak around 562 nm due to surface plasmon resonance of Au particles. However, when a small amount of Fe was added, the resonant absorption was quenched, and χ(3) was enhanced so that χ(3)/α was significantly increased. Our study suggests a method by which to design optical nonlinear materials with large figure of merits for practical application.