Nanocomposite thin films consisting of nanometer-sized Cu particles embedded in an amorphous Ba0.5Sr0.5TiO3 matrix (Cu:BST) on Al2O3 (0001) substrates were fabricated by an alternating pulsed laser deposition method. The nanocomposite films containing Cu nanoparticles with a volume fraction of more than 5.4% showed a characteristic surface plasmon resonance (SPR) absorption band at similar to 580 nm. The nonlinear optical properties of the Cu:BST nanocomposite film with a Cu volume faction of 5.4% were determined using the Z-scan method at the SPR wavelength. The magnitude of the third-order nonlinear susceptibility of the sample was calculated to be 9.737 x 10(-9) esu. (c) 2006 Elsevier B.V All rights reserved.