Optical phase conjugation in schott cdsse-doped glasses: Origin of the nonlinear response

We report results on optical phase conjugation in experimental CdSSe-doped glasses close to a quantumconfined resonance. The dispersion of the Kerr susceptibility is measured in a degenerate four-wave mixing experiment, and it is shown that the nonlinear response is quite different for experimental and commercial glasses. In particular, for the former the spectral dispersion of the nonlinearity exhibits an intensity dependence. The various results can be explained by a competition between three mechanisms corresponding to the saturation of the electronic transitions involved (volume and surface states) by taking into account the efficient trapping of carriers into deep impurity levels.