Metal nanoparticles-silica composites:: Z-scan determination of non-linear refractive index

Metal quantum-dot composite glasses can exhibit an enhanced optical Kerr susceptibility, chi((3)), whose real part is related to the n(1)(2) coefficient of the intensity-dependent refractive index. We used the Z-scan technique for measuring the n(2)(1)'s of micrometric composites films formed by copper with nanometer sized particles embedded in silica glass by means of radiofrequency magnetron sputtering technique, followed by thermal annealing in reducing atmosphere, to promote cluster growth. A single 6 ps long pulse at a repetition rate of 1 Hz was used to determine the picosecond fast (non-cumulative, electronic) response of the composites. We obtain n(2)(1) from (0.48 +/- 0.24) x 10(-11) to (2.0 +/- 1.0) x 10(-11) cm(2)/ W and beta of (3.1 +/- 1.6) x 10(-7) to (8.5 +/- 4.2) x 10(-7) cm/W in the explored range of Cu/SiO2 composition. (C) 2003 Elsevier B.V. All rights reserved.