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.