Nanocrystal size dependence of the third-order nonlinear optical response of Cu : Al2O3 thin films

Metal nanocomposite thin films formed by Cu nanocrystals embedded in an amo rphous Al2O3 host have been synthesized by pulsed laser deposition. The mea n nanocrystal diameter d was varied in the range 3.0+/-0.6 to 6+/-1 nm. The linear and nonlinear optical properties of the films were studied in the v icinity of the surface plasmon resonance and the size dependence of the thi rd-order nonlinear optical susceptibility of the metal nanocrystals has bee n determined. The observed dependence (1/d(3)) indicates that in the studie d diameter interval, the nonlinear response is due to quantum confinement e ffects in which the major contribution is associated with electronic intrab and transitions. (C) 1999 American Institute of Physics. [S0003-6951(99)017 19-2].