In this work, we have studied the concentration quenching of the 3H4→3F4 emission of Tm3+ doped lead-niobium-germanate glasses (GeO2-PbO-Nb2O5) for different Tm3+ concentrations (0.1, 0.2, 0.5, 1, 2, and 3 wt%). The emission spectra obtained under 798 nm excitation reveal the existence of energy transfer via cross-relaxation among Tm3+. As a result, the intensity of the infrared 3H4→3F4 emission at 1474 nm decreases in relation to that of the 1820 nm emission as concentration increases. The non-exponential character of the decays from the 3H4 level with increasing concentration, together with the dependence of the effective decay rates on Tm3+ concentration, indicate the presence of a dipole-dipole quenching process in the framework of a diffusion-limited regime.
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