Local environment of rare-earth dopants in silica-titania-alumina glasses:An extended x-ray absorption fine structure study at the K edges of Er andYb

We have applied extended x-ray absorption fine structure (EXAFS) spectrosco py to the K edge of rare earths (RE) in a study of the local environments o f diluted Er and Yb dopants in silicate glasses, prepared by sol-gel proces sing. Silica-titania-alumina glasses, doped with RE ions at and above the l uminescence quenching concentration were investigated and EXAFS spectra wer e recorded in a wide k range up to 160 nm(-1) not obtainable when working a t the L-III edge. No direct RE-RE correlations were found, providing a stro ng support for previous studies. A model of RE aggregation derived from the se observations is also discussed. (C) 2001 American Institute of Physics.