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

Abstract

Broadband 1.20μm emission originating from the Thulium (Tm3+): 1G4→3H4 transition was observed in Tm3+-doped gallogermanate glasses under 476.5nm excitation. The stimulated emission cross-section is calculated to be 2.85×10–21cm2 using 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 1.2μm wavelength region.