Anomalous temperature quenching of fluorescence in Pr3+ doped sulfide glass

Fluorescence from the 1D2 level of Pr3+-doped AsGaGeS glass is found to be strongly quenched with increasing temperature. A model for this quenching is proposed which involves energy transfer from the Pr3+ ions to near-band gap defect states in the host glass. Energy transfer from these defect states back to Pr3+ in the 1G4 state with an estimated efficiency of ≈10−3 is also observed. The occurrence of these energy transfer processes complicates quantum efficiency measurements made using a self-calibrating branching ratio technique. After accounting for this energy transfer, the quantum efficiency for the 1300 nm emission in Pr3+ doped AsGaGeS glass is found to be 0.48 rather than the previously obtained value of 0.55. No temperature quenching of the 1G4 level of Pr3+ is observed when this level is pumped directly. Nd3+ impurities in the same glass are much less strongly quenched than Pr3+ when pumping around 600 nm.