Luminescent properties of local atomic order of Er3+ and Yb3+ ions in aluminophosphate glasses

We report on an extended x-ray absorption fine structure (EXAFS) investigat ion on the local atomic order around rare earth (RE) ions in Er+Yb doped al uminophosphate glasses. Samples were obtained from the melt and the RE conc entration ranged from 0.5 to 5 wt. %. EXAFS data were analyzed within the m ultiple scattering formalism providing a detailed description of the atomic neighborhood in the first two shells. In particular, each RE in was found to be surrounded by similar to7 PO4 tetrahedra linked by corner O atoms. Fo r RE concentrations below and above the luminescence "quenching" value, no detectable variations are reported leading us to exclude the formation of R E clusters within the sensitivity of the technique. From the analysis of th e edge region a description of the density of free 5d states (linked to the radiative emission probability) is also obtained, which again shows no dif ference at the various RE concentrations. (C) 2001 American Institute of Ph ysics.