Quantum efficiency of Pr3+ doped transparent glass ceramics

The quantum efficiency of the 1.3 mu m transition in Pr3+ doped oxyfluoride transparent glass ceramics is measured using a self-calibrating fluorescence ratio technique. The measured value of 8%+/-1% is much higher than expected for Pr3+ in an oxide glass, and is consistent with the incorporation of the Pr3+ ions into the fluoride nanocrystals of the glass ceramic. Measured quantum efficiencies are compared with values calculated using the Judd-Ofelt theory, and it is found that the best agreement is obtained when fractional differences between calculated and measured oscillator strengths are minimized, rather than absolute differences. The Judd-Ofelt analysis is used along with a spectral analysis to show that excited-state absorption should not significantly reduce the gain around 1.3 mu m in these materials. The fluorescence ratio technique used to measure the quantum efficiency also provides information about ion-ion interactions at higher concentrations. It is found that the addition of the monovalent dopant Ag+ reduces the tendency of the Pr3+ ions to cluster, allowing higher concentrations of Pr3+ without significant concentration quenching. (C) 1998 American Institute of Physics. [S0021-8979(98)05703-X].