Artificial dielectrics:: Nonlinear properties of Si nanoclusters formed by ion implantation in SiO2 glassy matrix

The nonlinear optical properties of Si nanoclusters formed by ion implantation into an SiO2 glassy matrix and followed by annealing have been studied at lambda = 532 nm and lambda = 355 nm by use of Z-scan and pump-probe techniques. These have been compared to the nonlinear properties of laser-ablated Si films. At relatively large intensities (>1 MW/cm(2)) the absolute nonlinear values for these isolated nanoclusters were comparable to those obtained for laser-ablated samples although opposite in sign. Laser-ablated samples showed a much larger effect at relatively low intensities (<1 MW/cm(2)), while the ion-implanted films showed almost none. Lifetime constants were in the range of 3-5 ns for all samples. (C) 1998 American Institute of Physics. [S0021-8979(98)07324-1].