Enhanced emission of 2.9 μm from Ho^3＋/Pr^3＋ co-doped LiYF4 crystal excited by 640 nm

The use of Pr^3＋ co-doping for great enhancement of mid-infrared （mid-IR） emissions at 2.9 gm and 2.4 μm is investigated in the Ho^3＋/pr^3＋ co-doped LiYF4 crystals. With the introduction of Pr^3＋ ions, the fluorescence lifetime of Ho^3＋：sI7 level is 2.15 ms for Ho^3＋/pr^3＋co-doped crystal, and the lifetime for Ho^3＋ singly doped crystal is 17.70 ms, while the lifetime of H0^3＋：5I6 level decreases slightly from 2.1l ms for Ho^3＋：LiYF4 to 1.83 ms for Ho^3＋/pr^3＋：LiYF4. It is also demonstrated that the introduction of Pr3＋ greatly increases the mid-infrared emission of H03＋：5I6→5I7 which depopulates the H03＋：5I7 level, while it has little influence on the Ho^3＋：516 level, which is beneficial for greater population inversion and laser operation. The analysis on the decay curves of the 2.0 μm emissions in the framework of the Inokuti-Hirayama model indicates that the energy transfer from Ho^3＋ to Pr^3＋ is mainly from electric dipole-dipole interaction. The calculated efficiency of energy transfer from H0^3＋：5I7 to pr^3＋：3F2 level is 87.53% for Ho^3＋/pr^3＋ （1.02%/0.22%） co-doped sample. Our results suggest that the Ho^3＋/pr^3＋ co-doped LiYF4 single crystals may have potential applications in mid-IR lasers.