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

摘要

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~(10) W/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~(-9) esu and shows a systematic increase as the silicon nanocrystalline size decreases. This is due to quantum confinement effects.