Broadband 1.20 μm emission in Tm³⁺-doped and Tm³⁺/Tb³⁺, Eu³⁺codoped gallogermanate glasses

Broadband 1.20 μm emission originating from the Thulium (Tm3+):1G4→3H4transition was observed in Tm3+-doped gallogermanate glasses under 476.5 nm excitation. The stimulated emission cross-section is calculated to be 2.85 × 10-21cm2using the Füchtbauer-Ladenburg approach. Difficulty in the population inversion between the upper 1G4 and lower 3H4 levels resulting from the cross relaxation process Tm3+[1G4,3H6] → [3H4,3H5] was overcome by the incorporation of Terbium (Tb3+) and Europium (Eu3+) ions. A Judd-Ofelt analysis was performed based on the absorption spectrum and the derived intensity parameters (Ω2= 4.65 × 10-20, Ω4= 1.51 × 10-20, and Ω6= 1.42 × 10-20cm2) reveal a strong asymmetry and covalent environment between Tm3+ions and ligands in the host matrix. The results indicate that the Tm3+/ Tb3+, Eu3+codoping scheme is promising in the development of amplifiers and lasers operating at the relatively unexplored 1.2 μm wavelength region.