Concentration quenching of fluorescence from the (3P0 + 3P1) manifold in heavily-doped Pr3+: ZBAN glasses

Fluorescence waveforms from the (3P0 + 3P1) manifold in Pr3+ doped ZBAN glass at wavelengths of 520, 635 and 695 nm were measured for Pr3+ concentrations from 4 to 12 mol%. The waveforms were found to be non-exponential with decay rates rapidly increasing with Pr3+ concentration and independent of whether the 3P0 or the 3P1 level was excited. The multipolar energy transfer model was used to analyse the waveforms and this showed that concentration quenching was due to cross-relaxation by dipole–dipole interaction. The critical concentration, at which the cross-relaxation rate equals the intrinsic decay rate, was found to be of 2.06 × 1026 m−3 (1.20 mol%). There was no evidence of excitation diffusion for Pr3+ concentrations of up to 12 mol%.