Concentration dependence of visible luminescence from Pr3+-doped phosphate glasses.

To clarify the concentration dependence of visible fluorescence of Pr3+, a series of phosphate glass samples with Pr3+ concentration from 0.05 to 3.0 mol% were fabricated. Steady and dynamic spectroscopic characteristics of Pr3+-doped phosphate glasses were systematically investigated. When the Pr3+ concentration was small, only one visible fluorescence band can be observed at 596 nm, which was ascribed to the transition of 1D2 → 3H4. With increasing Pr3+ concentration from 0.05 to 0.5 mol%, since the multi-phonon relaxation rate of 3P0 was largely quicker than that of 1D2. Increasing Pr3+ concentration from 0.5 to 3 mol%, increasing two other fluorescence bands at 612 nm and 640 nm, which were assigned to the transitions of 3P0 → 3H6 and 3P0 → 3F2, respectively. It was due to the cross relaxation probability between [1D2: 1G4] and [3H4: 3F4] increased, which results in quicker decay rate of 1D2. The fluorescence lifetime of 1D2 decreased from 173 to 6 μs with increasing Pr3+ concentration from 0.1 to 3 mol%, which due to the cross relaxation probability between [1D2: 1G4] and [3H4: 3F4] increased, resulting in quicker decay rate of 1D2. Fitting the concentration dependence of fluorescence lifetime demonstrated that the cross relaxation arising from dipole-dipole interactions between Pr3+ ions.