Plasmon resonant absorption and third-order optical nonlinearity in Ag–Ti cosputtered composite films

A series of Ag/titanium oxide composite films with Ag atom concentration of 28%–82% were prepared by cosputtering technique. The scanning electron microscopy and the x-ray photoelectron spectroscopy studies reveal that metallic Ag nanoparticles with a size of 20–50nm disperse in titanium oxide. The plasmon resonance absorption peak of the embedded Ag nanoparticles shifts to about 860nm at Ag atom concentration of 42%, the nonlinear absorption coefficient βeff and the nonlinear refractive index γ are −1.4×105cm∕GW and 3.8cm2∕GW, respectively, which were measured by the Z-scan technique at 790nm with a peak irradiance of 1.8GW∕cm2. The corresponding third-order susceptibility χ(3) is about 4.7×10−7esu.