Third order optical nonlinearity investigation of germanium quantum dots embedded in silica matrix

Multilayered germanium nanocrystals embedded in silica (SiO₂) matrices are fabricated by using the radio frequency magnetron co-sputtering technique. Transmission electron microscopy shows germanium (Ge) nanocrystals are confined in the (Ge+SiO₂) layers in the silica thin films. Linear optical absorption coefficients at different wavelengths and the energy gap of the films are calculated based on absorbance measurement data. Photoluminescence emission property is also characterized. Using the open aperture z-scan technique, we have also measured nonlinear absorption and computed the imaginary part of third-order optical susceptibility of these samples.