Quantum efficiency of Pr3+ doped transparent glass ceramics

The quantum efficiency of the 1.3 μm 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 μm 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.