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Tb3+ ions doped optical materials have emerged as gain media for green fiber lasers. Dy3+ ions were proposed as a sensitizer of Tb3+ ions in glasses to increase the excitation efficiency, yet a systematic understanding of the impact of Dy3+ doping on spectroscopic and physiochemical properties of glasses remains lacking. Here, using Tb3+/Dy3+ doped fluoride glass as a model system, we reveal that Dy3+ doping not only enhances Tb3+ emission intensity, but also increases the thermal stability of fluoride glasses. Detailed spectroscopic characterizations indicate that co-doping Dy3+ ions boosts visible luminescence intensity of Tb3+ ions in fluoride glasses due to sensitization of Tb3+ by Dy3+ ions. Importantly, we deeply research the energy transfer process, ascertain several important factors affecting energy transfer efficiency and propose optimal doping concentrations of Tb3+ and Dy3+ ions for visible emission. We envisage that our finding provides a new perspective for the synthesis of Tb3+-doped fluoride glasses with enhanced thermal stability, and may be extended for the fabrication of Tb3+-activated optical fibers.

A series of Dy3+/Tm3+ single- and co-doped phosphate glasses with high moisture resistance and thermal stability was prepared by a conventional melt-quenching method. Under 365-nm ultraviolet (UV) light excitation, a white light with a chromatic coordinate of (0.3300, 0.3439), which is very close to the standard white light, could be obtained. The luminescence characteristics and energy transfer mechanism between the Dy3+ and Tm3+ ions were studied, and the fluorescence lifetime revealed the existence of the energy transfer processes. Furthermore, the Dy3+/Tm3+ co-activated glasses exhibited high moisture resistance, the emission peaks of 450, 480 and 572 nm remained at the original intensity of 99.2%, 99.9% and 99.9% of its original intensity after immersion in water for 120 h. At the same time, the luminescence intensity of the sample at 500 K can be maintained at a minimum of 85% of its intensity at room temperature, indicating the good thermal stability of the glasses. Overall, the prepared phosphate glasses have the potential to be applied in UV-based white-light-emitting diodes.

This paper studied the de-sensitization effect of Pr 3+ and Ho 3+ to Er 3+ :2.7 μm emission. Results show that both Pr 3+ and Ho 3+ are effective de-sensitizers, while great differences exist between them because of their non-phonon and phonon assisted energy transfer (ET) mechanisms. Ho 3+ depresses the 2.65 μm emission while Pr 3+ strengthens it greatly. ET coefficient indicates that Pr 3+ performs ten times higher 4 I 13/2 depletion ability than Ho 3+ . In Er/Ho glasses, about 1/10 energy back transfers to 4 I 13/2 level, which partially counterweights the depopulation of 4 I 13/2 level. The high absorption cross section of Ho 3+ is the reason for the larger 4 I 11/2 → 5 I 6 ET coefficient. Line strength and spontaneous radiation probability of 4 I 11/2 → 4 I 13/2 transition enhance moderately in E, E/H and E/P order, proving that the de-sensitizers promote the 2.7 μm transition positively. Long lifetime of Ho 3+ : 5 I 6 / 5 I 7 brings many problems, such as energy back transfer and strengthened upconversion, which also implies that the interactions of the particles obstruct the effective 4 I 11/2 → 4 I 13/2 transition correspondingly.