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.

Keywords

Lower Laser Level / Laser Level / Emission Cross Section / Fluorescence Decay Curve / Oxyfluoride Glass

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This work has been supported by the National Natural Science Foundation of China (Nos.51272109 and 50972061), the Natural Science Foundation of Zhejiang Province (No.R4100364), the Natural Science Foundation of Ningbo in Zhejiang Province of China (No.2012A610115), and K. C. Wong Magna Fund in Ningbo University.