A NOVEL METHOD FOR UNIFORM DISPERSION OF THE RARE-EARTH IONS IN SIO2 GLASS USING ZEOLITE-X

A novel method for uniform dispersion of the rare earth ions in SiO2 g lass is presented. Nd doped SiO2 laser glass has been made by aluminum co-doping to avoid quenching due to Nd clustering. Previous works wit h aluminum co-doping were passive methods because uniform dispersion o f the rare earth ions in SiO2 glass depended only on aluminum co-dopin g effect. Concentration quenching of Nd laser glass is explained by cr oss-relaxation process and depends on Nd-Nd distance in the glass. The shorter the Nd-Nd distance the stronger is quenching, so the distance should be greater than some minimum. Homogeneous rare earth doped SiO 2 glass is achieved by a modified sol-gel method using zeolite X. Zeol ite X (Na-86[(AlO2)(86). (SiO2)(106)] . 264H(2)O, faujasite-type struc ture) is a suitable material because Nd ions are selectively exchanged at the D6R segment structure in zeolite X, and the distance between N d ions in the D6R is 0.88 nm. This distance is three times larger than the critical range of cross-relaxation process which causes quenching . If the Nd-Nd distance is kept at 0.88 nm, the ratio of cross-relaxat ion probability to radiative decay probability will be 0.23%. Quantum yield is an adequate quantity for confirming uniform dispersion of the rare earth ions in Nd doped laser media. For a newly prepared Nd dope d SiO2 glass using zeolite X, quantum yield increased to 50 +/- 3.4% a t 1.0 wt%, while an ordinary produced one was 7 +/- 0.5%. (C) 1997 Els evier Science B.V.