Crystal field studies in Eu3+ doped Bi12SiO20 and Bi12SiO20: V5+ single crystals

Site-selective laser spectroscopy investigations of Eu3+ in Bi12SiO20 (BSO) and Bi12SiO20:V5+ (BSO:V) single crystals have been carried out. The line narrowed fluorescence shows the existence of a single crystal field site for the rare earth in BSO whereas in BSO:V five different crystal field sites for Eu3+ may exist, which depend on the vanadium concentration. The number of Stark components observed in D-5(0)--> F-7(J) transitions corresponds to a complete absence of degeneracy in F-7(J) multiplets and indicates a symmetry C-2v or lower for these optically active centres. Simulations of the sequence of Eu3+ energy levels for each of the five observed sites have been worked out by using the single-particle crystal-field theory. The nature of the new active optical sites has also been investigated by comparing the phenomenological crystal-field parameters with those calculated by a semi-empirical model which takes into account the distortions of the oxygen bonds produced by the presence of V5+. (C) 2001 Elsevier Science B.V. All rights reserved.