Sensitizing effect of Tm3+ on 2.9 mu m emission from Dy3+-doped Ge25Ga5S70 glass

Energy transfer mechanisms and the effect of Tm3+ addition on the intensity of the Dy3+:2.9 mu m emission from Ge25Ga5S70 glass were investigated. Intensity of the 2.9 mu m fluorescence from Dy3+ increased with increasing Tm3+ content when the Dy3+ concentration remained constant, which indicates the presence of an efficient energy transfer between Tm3+ and Dy3+. A decrease in the measured lifetimes of the Tm3+:F-3(4) level and a wide spectral overlap between the Tm3+:1.8 mu m emission and the absorption of Dy3+:H-6(15/2)-->H-6(11/2) also supported the proposed energy transfer scheme. Analyses of the emission intensities and decay times suggested that a direct energy transfer from the Tm3+:F-3(4) level to Dy3+:H-6(11/2) level occurred after a fast diffusion-limited migration fo the excitation energy among Tm3+.