Downconversion in Pr3+ - Yb3+ co-doped ZBLA fluoride glasses

Fluorozirconate ZBLA glasses with molar composition 57ZrF4-34BaF2-5LaF3-4AlF3-0.5PrF3-xYbF3 (from x=0 to10) were synthesized to evaluate the rate of the conversion of visible photons into infrared photons. The emission spectra in the near infrared (NIR) at 950-1100 nm and the luminescence decays in the visible and NIR indicate an energy transfer from Pr3+ to Yb3+ upon blue excitation of Pr3+ at 440 nm. The energy transfer efficiency increases with Yb3+ concentration to reach 86% with 0.5Pr3+ - 10Yb3+ co-doping (in mol%). However, the quenching of the Yb3+ emission strongly reduces the efficiency of the downconversion process: the decay time values decrease from 600 ms (x=0.5 mol%) to 85 ms (x=10 mol%).