KINETICS OF HOLOGRAPHIC REFRACTIVE-INDEX GRATINGS IN RARE-EARTH-SENSITIZED GLASSES

Diffusion of small modifier cations over distances large compared to t he interatomic spacing is used to account quantitatively for the kinet ics of photoinduced refractive-index gratings that can be holographica lly written in rare-earth-doped glasses. A model is developed that inc ludes diffusion activated by nonradiative relaxation of the rare-earth sensitizers, drift under the space-charge field or externally applied fields, and trapping of the mobile modifiers. In this model the refra ctive-index contrast of the grating arises from the modulation of the concentration of small modifiers. The model accounts well for experime nts on Eu3+-doped silicate glasses reported here. [S0163-1829(98)04525 -1].