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 H-3(4) -> F-3(4) and F-3(4), -> H-3(6) emissions of Tm3+-doped lead niobium-germanate glasses (GeO2-PbO-Nb-2-O-5) 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 H-3(4) -> F-3(4) 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 H-3(4) 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 F-3(4) -> H-3(6) emission at 1820 nm can be attributed to limited diffusion within the active centers. (c) 2006 Elsevier B.V. All rights reserved.