Z-scan Studies on the Third-order Optical Nonlinearity of Au Nanoparticles Embedded in TiO2

Nonlinear optical properties of gold nanoclusters have attracted wide attention, owing to their potential use as non-linear optical devices.1 In the surface plasmon resonance (SPR) absorption region, the material exhibits large optical nonlinearities and ultrafast time response.2-5 The SPR peak position of spherically shaped gold particles embedded in dielectrics can be predicted by the Mie theory: ε1(ωs) + 2εm (ωs) = 0 (1) where ε1 is the real part of the dielectric constant of the metal particle, and εm the dielectric constant of the surrounding dielectrics, and ωs the surface plasmon resonance fre-quency.1 The peak position of the SPR absorption band of Au nano-clusters in common SiO2 glass (ε ≈ 2.3) occurs around 520 nm. As the dielectric constant of the matrix increases, th