Fluorescence dynamics of Tb3+ and Tb3+/Ho3+ doped phosphate glasses

UV absorption and fluorescence analysis of Tb3+ in phosphate glass is carried out by Judd–Ofelt method with emphasis on the 5D4→7F55D4→7F5 lasing transition. Branching ratios, peak emission cross-sections for 5D4→7Fj(j=3,4,5and6) transitions and lifetime of 5D45D4 level of Tb3+ are calculated using Judd–Ofelt intensity parameters. Furthermore, fluorescence dynamics of the 5D45D4 level of Tb3+ ion in phosphate glasses co-doped with Ho3+ were experimentally investigated with classical Forster–Dexter model for direct cross-relaxation type energy transfer between Tb3+ (donor) and Ho3+ (acceptor). The energy transfer rates between Tb3+ and Ho3+ in phosphate glasses were calculated on the basis of experimental measurements. These measurements were performed for 1 wt.% of Tb3+ and Ho3+ concentration ranging from 0 to 3 wt.%. The results show that energy transfer occurs between the 5D4 terbium and 5F3 holmium levels and is a phonon-assisted dipole–dipole interaction.