Crystal field calculations of Yb3+-doped double borate crystals for laser applications

Crystal field effects are very important as far as laser performances of Yb-doped materials are concerned. In order to simplify the interpretation of low-temperature spectra, two tools derived from a careful examination of crystal field interaction are presented. Both approaches are applied in the case of new Yb-doped materials, namely Sr3Y(BO3)3 (BOYS) and Ba3Lu(BO3)3 (BLuB). The 2F7/2 splitting is particularly large in these materials and favorable to a quasi-3-level laser operating scheme. Calculations performed using the point charge electrostatic model (PCEM) for these compounds and using a consistent set of effective atomic charges confirm the experimental results. This should permit the use of this model in a predictive approach.