Improved 2 µm broadband luminescence in Tm³⁺/Ho³⁺ doping tellurite glass

Tm³⁺/Ho³⁺ doping tellurite glasses (TeO₂-ZnO-La₂O₃) were prepared by applying melt-quenching technique, and the ∼2.0 µm band luminescence characteristics were examined. A broadband and relatively flat luminescence at 1600 to 2200 nm was observed in the tellurite glass co-doped by 1.0 mol% Tm₂O₃ and 0.085 mol% Ho₂O₃ under the excitation of 808 nm laser diode (LD), which is the result of spectral overlapping of 1.83 µm band of Tm³⁺ ions and 2.0 µm band of Ho³⁺ ions. Further, about 103% enhancement was acquired after the introduction of 0.1 mol% CeO₂ and 7.5 mol% WO₃ at the same time, which is primarily caused by the cross-relaxation between Tm³⁺ and Ce³⁺ ions together with the enhanced energy transfer from the Tm³⁺:³F₄ level to Ho³⁺:⁵I₇ level due to the increase in phonon energy. Spectral characteristics associated with the radiative transition of Ho³⁺ and Tm³⁺ ions on the basis of Judd-Ofelt theory, and the fluorescence decay behaviors after the addition of Ce³⁺ ions and WO₃ component were analyzed to understand the broadband and luminescence enhancement. The findings in this work indicate that tellurite glass with optimal Tm³⁺-Ho³⁺-Ce³⁺ tri-doping combination and appropriate amount of WO₃ is a prospective candidate for broadband optoelectronic devices operated in the infrared bands.