[en] The measurements of the optical nonlinearities of Ge and Si implanted glasses is reported. Analytic techniques employed included Rutherford backscattering, using 2.0 MeV He ions, optical absorption and transmission electron microscopy. The results indicate that the presence of implanted species changed the absorption spectra and that the magnitude of the optical nonlinearities for Ge and Si implanted samples are quite different. A possible explanation is the difference in absorption coefficient that may be amplified by quantum confinement effects which causes the indirect energy gaps of Ge and Si nanocrystals to increase as particle size decreases