Preparation and femtosecond third-order nonlinear optical properties of Cu/SiO2 composite thin films

A multitarget sputtering method was applied to embed Cu particles in SiO2 glass thin films (Cu/SiO2 films) with a high concentration of Cu particles (18 at.%). In the optical-absorption spectra of the as-deposited Cu/SiO2 films, the absorption peak due to the surface plasmon resonance of Cu particles was observed around 580 nm. The imaginary part of the third-order nonlinear susceptibility, \Im[chi((3))]\, exhibited a peak at the absorption peak, and the maximum value was estimated to be 1.8 x 10(-10) esu in the femtosecond time region. The nonlinear response time derived from the recovery time of the nonlinear absorption of the film was estimated to be 1.4 ps at the absorption peak of the surface plasmon.