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 amorphous Al2O3 host have been synthesized by pulsed laser deposition. The mean 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 vicinity of the surface plasmon resonance and the size dependence of the third-order nonlinear optical susceptibility of the metal nanocrystals has been determined. The observed dependence (1/d(3)) indicates that in the studied diameter interval, the nonlinear response is due to quantum confinement effects in which the major contribution is associated with electronic intraband transitions. (C) 1999 American Institute of Physics. [S0003-6951(99)01719-2].