Nonlinear optical properties of silicon nanocrystals grown by plasma enhanced chemical vapour deposition

The real and imaginary parts of third-order nonlinear susceptibility χ (3) have been measured for silicon nanocrystals embedded in SiO 2 matrix, formed by high temperature annealing of SiO x films prepared by plasma-enhanced chemical vapor deposition. Measurements have been performed using a femtosecond Ti-sapphire laser at 813 nm using the Z-scan technique with maximum peak intensities up to 2×10 10W/cm 2. The real part of χ (3) shows positive nonlinearity for all samples. Intensity-dependent nonlinear absorption is observed and attributed to two-photon absorption processes. The absolute value of χ (3) is on the order of 10 -9esu and shows a systematic increase as the silicon nanocrystalline size decreases. This is due to quantum confinement effects. © 2002 American Institute of Physics. © 2002 American Institute of Physics.