The use of Pr3+ codoping for enhancement of the Ho3+:5I6 →5I7 mid-IR emissions were investigated in the LiLuF4 crystal for the first time. It was found that Pr3+ greatly increased Ho3+ 2.9 μm emission by depopulating the Ho3+:5I7 level while having little influence on the Ho3+:5I6 level, leading to greater population inversion. The energy transfer efficiency from Ho3+:5I7 to Pr3+:3F2 is calculated to be 88%. Based on Judd-Ofelt theory, the 2.9 μm emission cross section is calculated to be 1.91×10(-20) cm2, and the gain property of the Ho3+:5I6 →5I7 transition is discussed. We propose that the Ho, Pr:LiLuF4 crystal may be a promising material for 2.9 μm laser applications.
A Ho³⁺-doped PbF₂ mid-IR laser crystal was successfully grown using the vertical Bridgman method. An intense 2.8 μm emission in Ho:PbF₂ crystal was observed for the first time. By analyzing the absorption and emission measurements of the Ho:PbF₂ crystal with the Judd-Ofelt theory, the intensity parameters Ω(2,4,6), exited state lifetimes, branching ratios, and emission cross-sections were calculated. It is found that the Ho:PbF₂ crystal has high fluorescence branching ratio (20.99%), large emission cross section (1.44×10⁻²⁰ cm²), long fluorescence lifetime (5.4 ms), and high quantum efficiency (88.4%) corresponding to the stimulated emission of Ho³⁺: ⁵I₆→⁵I₇ transition. The structure of Ho:PbF₂ crystal was also analyzed by the Raman spectrum, and it was found that the Ho:PbF₂ crystal possesses low phonon energy of 257 cm⁻¹. We propose that the Ho:PbF₂ crystal may be a promising material for 2.8 μm laser applications.
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