Effect of concentration on the infrared emissions of Tm3+ ions in lead niobium germanate glasses

In this work, we have studied the effect of concentration on the 3H4 → 3F4 and 3F4 → 3H6 emissions 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%) and at different temperatures between 10 K and 295 K. 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 emission at 1820 nm, as concentration increases. The non-exponential character of the decays from the 3H4 level with increasing concentration, together with the dependence of the quenching rate on Tm3+ concentration, indicate the presence of a dipole–dipole quenching process in the framework of a diffusion-limited regime. The self-quenching of the 3F4 → 3H6 emission at 1820 nm can be attributed to limited diffusion within the active centers.