Luminescence quenching by OH groups in highly Er-doped phosphate glasses

Highly (up to 4 mol% Er2O3) Er-doped phosphate bulk glasses have been prepared by common glass-melting techniques. Afterwards, a heat treatment was performed on the as-melted samples. The photoluminescence lifetime of Er ions for the 4I132–4I152 transition increases substantially, typically from 3 ms up to 7 ms for a sample doped with 2 mol% Er2O3, due to the heat treatment. The increase of the lifetime is ascribed to a decrease in concentration of hydroxyl groups incorporated in the glass, which is confirmed by IR absorption spectroscopic measurements. The photoluminescence peak intensity also increases because of drying by a factor of 3 to 7 depending on glass composition. Based on electric dipole-dipole interaction theory, the luminescence concentration quenching mechanism by hydroxyl groups is modelled. The model predicts that more than half of the hydroxyl groups in the glass is coupled to Er ions. The influence of the glass structure and role of Al3+ on the Er3+ luminescence is studied by infrared spectroscopy.