Nd3+→Yb3+ energy transfer in a codoped metaphosphate glass as a model for Yb3+ laser operation around 980nm

A complete spectroscopic investigation of a metaphosphate glass with composition Pb(PO3)(2) doped with various amounts of Nd3+ and Yb3+ ( 1 up to 10 at.%) is reported. Efficient Nd3+ --> Yb3+ energy transfers occur both radiatively and non-radiatively, the latter being dominant and partly resonant and partly phonon-assisted by phonons of the order of 950 cm(-1), which fits well with the reported Raman spectrum of the material. These transfers mainly concern the F-4(3/2) --> I-4(9/2) emission and the F-2(7) --> F-2(5/2) absorption transitions of the Nd3+ and Yb3+ ions around 900 nm, respectively. They are analysed both via spectral and temporal data. The results show that about 5% Nd3+ and 5% Yb3+ ions have to be incorporated to reach energy transfers exceeding about 65%, which is in agreement with data recently reported in the case of a YAl3(BO3)(4) crystal. Simulations based on the obtained data show that laser thresholds of a few tens of mW should be easily attainable by operating the materials in a channel waveguide configuration.