Abstract
The real and imaginary parts of third-order nonlinear susceptibility χ(3) have been measured for silicon nanocrystals embedded in SiO2 matrix, formed by high temperature annealing of SiOx 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 2×1010 W/cm2. 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 10−9 esu and shows a systematic increase as the silicon nanocrystalline size decreases. This is due to quantum confinement effects.
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