Fluorescence dynamics of Tb 3+ and Tb 3+/Ho 3+ doped phosphate glasses

Abstract

UV absorption and fluorescence analysis of Tb 3+ in phosphate glass is carried out by Judd–Ofelt method with emphasis on the 5 D 4 → 7 F 5 lasing transition. Branching ratios, peak emission cross-sections for 5 D 4 → 7 F j ( j = 3 , 4 , 5 and 6 ) transitions and lifetime of 5 D 4 level of Tb 3+ are calculated using Judd–Ofelt intensity parameters. Furthermore, fluorescence dynamics of the 5 D 4 level of Tb 3+ ion in phosphate glasses co-doped with Ho 3+ were experimentally investigated with classical Forster–Dexter model for direct cross-relaxation type energy transfer between Tb 3+ (donor) and Ho 3+ (acceptor). The energy transfer rates between Tb 3+ and Ho 3+ in phosphate glasses were calculated on the basis of experimental measurements. These measurements were performed for 1 wt.% of Tb 3+ and Ho 3+ concentration ranging from 0 to 3 wt.%. The results show that energy transfer occurs between the 5D 4 terbium and 5F 3 holmium levels and is a phonon-assisted dipole–dipole interaction.