Abstract: Bi, Tm singly doped and Bi/Tm co-doped titanate glasses were prepared by the conventional melt quenching method. The enhanced emission of Tm³⁺: ³H₄→³F₄ transition at ~1485 nm, and the quenched emission of Tm³⁺: ³F₄→³H₆ transition at ~1810 nm were observed in Bi/Tm co-doped glasses under 808 nm excitation. Under 980 nm excitation, no Tm-relevant emission was observed in Tm singly doped glasses, while the emission of Tm³⁺: ³F₄→³H₆ transition at ~1810 nm was observed in Bi/Tm co-doped glasses. These results indicated that the energy transfer occurred between active Bi ions and Tm³⁺ in Bi/Tm co-doped glasses, in which the energy corresponding to Bi-related emission level excited the Tm³⁺ from ³F₄ to the 3H4 level under 808 nm excitation and from ³H₆ to the ³H₅ level under 980 nm excitation. The energy transfer processes were studied based on the Inokuti-Hirayama model, and the energy transfer of electric dipole-dipole interaction was confirmed to be dominant in Bi/Tm co-doped glasses. The energy transfer efficiency from Bi to Tm ions was estimated to be ~60% from the obtained lifetime of emission. Broadband emission covering 1200-1600 nm indicates Bi/Tm co-doped titanate glasse as potential material for broadband optical fiber amplifiers and tunable lasers.

Key words: near-infrared emission, active Bi ions, Tm ions, Inokuti-Hirayama model