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 g lass 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 fil ms, the absorption peak due to the surface plasmon resonance of Cu particle s was observed around 580 nm. The imaginary part of the third-order nonline ar 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 femtose cond time region. The nonlinear response time derived from the recovery tim e of the nonlinear absorption of the film was estimated to be 1.4 ps at the absorption peak of the surface plasmon.