REFRACTIVE-INDEX GRATINGS IN RARE-EARTH-DOPED ALKALINE-EARTH GLASSES

Four-wave-mixing techniques were used to produce permanent laser-induced refractive index gratings in Eu3+ -doped silicate glasses. These gratings are associated with a thermally induced change in the local glass structure at the site of the Eu3+ ions, leading to a double-minimum potential well for the electronic energy levels of the Eu3+ ions. The effects on the characteristics of the permanent laser-induced gratings produced by changing the divalent modifier ions of the glass host are reported and a theoretical model is presented to explain the physical origin of the change in the refractive index of the material.