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 implantat ion 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 tech niques. These have been compared to the nonlinear properties of laser-ablat ed Si films. At relatively large intensities (>1 MW/cm(2)) the absolute non linear values for these isolated nanoclusters were comparable to those obta ined for laser-ablated samples although opposite in sign. Laser-ablated sam ples showed a much larger effect at relatively low intensities (<1 MW/cm(2) ), while the ion-implanted films showed almost none. Lifetime constants wer e in the range of 3-5 ns for all samples. (C) 1998 American Institute of Ph ysics. [S0021-8979(98)07324-1].