Enhanced emission of 2.9 μm from Ho3+/Pr3+ co-doped LiYF4 crystal excited by 640 nm

Abstract

The use of Pr3+ co-doping for great enhancement of mid-infrared (mid-IR) emissions at 2.9 μm and 2.4 μm is investigated in the Ho3+/Pr3+ co-doped LiYF4 crystals. With the introduction of Pr3+ ions, the fluorescence lifetime of Ho3+:5I7 level is 2.15 ms for Ho3+/Pr3+co-doped crystal, and the lifetime for Ho3+ singly doped crystal is 17.70 ms, while the lifetime of Ho3+:5I6 level decreases slightly from 2.11 ms for Ho3+:LiYF4 to 1.83 ms for Ho3+/Pr3+:LiYF4. It is also demonstrated that the introduction of Pr3+ greatly increases the mid-infrared emission of Ho3+:5I6→5I7 which depopulates the Ho3+:5I7 level, while it has little influence on the Ho3+:5I6 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 Ho3+ to Pr3+ is mainly from electric dipole-dipole interaction. The calculated efficiency of energy transfer from Ho3+:5I7 to Pr3+:3F2 level is 87.53% for Ho3+/Pr3+ (1.02%/0.22%) co-doped sample. Our results suggest that the Ho3+/Pr3+ co-doped LiYF4 single crystals may have potential applications in mid-IR lasers.