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2 at.% Tm, xat.% Dy:Y 2 O 3 (x = 0, 0.1, 0.5 and 1) transparent ceramics were fabricated via vacuum sintering. The microstructural properties of the prepared ceramics were determined using XRD and SEM. The absorption cross-section of 2 at.% Tm, 1 at.% Dy:Y 2 O 3 ceramic was 0.53 × 10−20 cm2 with the FWHM of 43.59 nm. The increased cross-section originates from a large overlapping range appearing in the absorption spectrum of the Dy3+:6H 15/2 → 6F 5/2 and Tm3+:3H 6 →6H 4 transitions. The J-O intensity parameters Ω 2 , Ω 4 and Ω 6 and the fluorescence characteristics of the pivotal luminescent level of the Dy3+ ions were investigated. Under 793 nm excitation, the emission cross section of the Tm,Dy:Y 2 O 3 ceramic at 3094 nm was 3.63 × 10−21 cm2 with the FWHM of 355 nm. The fluorescence lifetimes of Dy3+:6H 13/2 level of 2 at.% Tm, xat.% Dy:Y 2 O 3 (x = 0.1, 0.5 and 1) ceramics were fitted to be 357 μs, 282 μs and 149 μs, respectively. In order to explore the quenching mechanism of Tm3+:3F 4 level, the fluorescence lifetimes of Tm3+:3F 4 of the 2 at.% Tm, xat.% Dy:Y 2 O 3 ceramics (x = 0, 0.1, 0.5 and 1) were measured to be 4.878 ms, 462 μs, 104 μs and 61 μs, respectively. The possible energy transfer mechanisms between Tm3+ and Dy3+ ions are discussed. The results show that adding Tm3+ ions to Dy:Y 2 O 3 ceramics can effectively enhance the 2.9 μm MIR through energy transfer. [ABSTRACT FROM AUTHOR]

• After co-doping Tb3+ ions, the Ω4/Ω6 increased 1.57 from to 1.66. • The branching ratios of the 3H 4 →3F 4 transition also strengthened. • The decay curve of 3F 4 level doped with different Tb3+ ions concentration decreased. • Tb3+ ion is a productive deactivator that could reduce the filling of 3F 4 mainfold and enhance the emission of 3H 4 →3F 4 transition. Tm3+ and Tb3+ co-doped Y 3 Al 5 O 12 (YAG) ceramics were fabricated by high temperature solid state reaction under oxygen sintering. The absorption spectra, fluorescence spectra and fluorescence decay curves of Tm,Tb:YAG ceramics were measured. The spectral parameters of Tm,Tb:YAG ceramic were calculated. The lifetimes of Tm3+:3F 4 level of Tm,Tb:YAG ceramics were calculated to be 11.28, 2.12, 1.24, 0.63 and 0.49 ms for the Tb3+ doping concentration of 0, 0.1, 0.2, 0.35 at 0.5 at%, respectively. The co-doping Tb3+ ion is a productive deactivator that could reduce the filling of 3F 4 mainfold and enhance the emission of 3H 4 →3F 4 transition. These results indicate that the addition of Tb3+ ions in Tm,Tb:YAG ceramic could be a promising technique for laser operation around 1.5 µm. [ABSTRACT FROM AUTHOR]