Enhancement mechanisms of Tm³⁺-codoping on 2 µm emission in Ho³⁺ doped fluoroindate glasses under 888 nm laser excitation

Ho3+ doped and Ho3+/Tm3+ co-doped fluoroindate glass samples were prepared and their emission properties were compared. Under 888 nm laser excitation, the emission at 2µm of Ho3+ ions with co-doping 2 mol% Tm3+ ions had a 2.9-fold improvement compared with that of Ho3+ doped. The absorption and emission spectra, and energy level lifetime of Ho3+/Tm3+ co-doped glass samples were measured to analyze the energy transfer processes and enhancement mechanisms. The luminescence intensity at 2µm can be greatly increased due to the bidirectional energy transfer between Tm3+ and Ho3+ ions