采用高温熔融法制备了单掺Tm3+和Tm3+/Ho3+共掺碲酸盐玻璃, 测试了808 nm激光泵浦下玻璃的红外和上转换荧光光谱。 Tm3+/Ho3+共掺碲酸盐玻璃上转换荧光光谱主要由695 nm红光、 544 nm绿光、 474 nm蓝光和740 nm红光四个发光带组成。 通过分析样品的光谱性能和能量转换机制, 发现很少报道的740 nm红光可能是由Tm3+: 1D2 →3F2, 3能级跃迁产生的。 在掺杂0.5 mol％ Tm2O3的样品中添加0.3 mol％ Ho2O3, 695 nm红光、 740 nm红光和474 nm蓝光等上转换发光强度明显增大, 大约分别是单掺0.5 mol％ Tm2O3样品中发光强度的3倍, 2.5倍和14倍。 这些情况说明存在着强烈的Ho3+→Tm3+反向能量传递。 单掺Tm3+碲酸盐玻璃中1D2能级(发射740 nm红光)上的粒子集居主要来源于合作上转换(CU)过程, 而3F2, 3能级(发射695 nm红光)上的粒子集居除了来源于CU过程之外, 还有740 nm红光的发射和1G4能级上部分粒子的无辐射跃迁(1G4→3F2, 3)两条途径, 因此样品中695 nm红光强度明显要大于740 nm红光强度。 通过交叉驰豫作用CR2和CR3以及反向共振能量转移RET2, Tm3+/Ho3+共掺碲酸盐玻璃中Tm3+的1G4能级(发射474 nm蓝光)上的粒子集居数比单掺Tm3+时出现了净增加。 Tm3+的1G4能级上粒子集居数的增加可能进一步强化了该能级的无辐射跃迁、 740 nm红光的发射以及CU过程, 并进而促使Tm3+的3F2, 3能级上的粒子集居。 所以, 当Tm3+/Ho3+共掺碲酸盐玻璃与单掺Tm3+碲酸盐玻璃中掺杂相同浓度的Tm3+时, 前者的红光和蓝光等上转换荧光强度均比后者要大。 本文还研究了Tm3+之间以及Tm3+与 Ho3+之间的交叉弛豫和能量传递等效应, 并进一步探讨了Tm3+与 Ho3+之间的能量转换机制。

The Tm3+ single-doped and Tm3+/Ho3+ co-doped tellurite glasses are prepared by traditional melt quenching technique. The synthesized glasses were characterized with infrared and up-conversion fluorescence spectra has been investigated in terms of the excitation of 808 nm laser, and the up-conversion fluorescence composed of four emission bands centering around 695, 544, 474 and 740 nm wavelengths, respectively. The 740 nm emission band seldom reported is possibly assigned to the Tm3+: 1D2→3F2, 3 transition by analyzing the spectra properties of the glass samples and relevant energy transfer mechanism. The intensities of 740, 695 and 474 nm emission in the tellurite glass at the concentration of 0.5 mol% of Tm2O3 and 0.3 mol% of Ho2O3 are almost 3, 2.5 and 14 times larger than those in the tellurite glass at the concentration of 0.5 mol% of Tm2O3, respectively. These obviously indicate that there is backward energy transfer from Ho3+ to Tm3+. The population for the energy level 1D2 (emitting 740 nm red) of Tm3+ in Tm3+ single-doped tellurite glass is significantly originated from cooperative up-conversion (CU). However, the population for the energy level 3F2, 3 (emitting 695 nm red) of Tm3+ is not only resulted from the process of CU, but also from the 1D2→3F2, 3 transition and the relaxation of the level 1G4 of Tm3+. Hence, the intensity of 695 nm emission is evidently higher than that of 740 nm emission in the samples. Because of the cross relaxation CR2 and CR3, as well as backward resonant energy transfer RET2, there is a net increase of population for the level 1G4 (emitting 474 nm blue) of Tm3+ in the Tm3+/Ho3+ co-doped tellurite glass compared to the Tm3+ single-doped tellurite glass while the two glasses are conformed with the concentration of Tm3+. The net increase of population for the level 1G4 of Tm3+ is possible to reinforce the multi-phonon relaxation process of this level, emission of 740 nm red light, as well as CU process, and further enhance the population for the level 3F2, 3 of Tm3+. Therefore, the intensities of red and blue fluorescence in the Tm3+/Ho3+ co-doped tellurite glass are clearly greater than those in the Tm3+ single-doped tellurite glass. The effects of cross relaxation and energy transfer between Tm3+ and Ho3+ are studied, while the energy transfer mechanism between Tm3+ and Ho3+ is also further discussed in the work.