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The Ho~(3+)/Pr~(3+) co-doped Na YF4 single crystals with various Pr~(3+) concentrations and constant Ho~(3+) molar percentage of ~1% were grown by an improved Bridgman method.Compared with the Ho~(3+) single-doped Na YF4 crystal,an obviously enhanced emission band at 2.85 μm is observed under 640 nm excitation.The Judd-Ofelt strength parameters(?2,?4 and ?6) are calculated,the radiative transition probabilities(A),the fluorescence branching ratios(β) and the radiative lifetime(τrad) are obtained in the meantime.The energy transfer from Pr~(3+) to Ho~(3+) and the optimum fluorescence emission of Ho~(3+) ions around 2.85 μm are investigated.Moreover,the maximum emission cross section of above samples at 2.85 μm is calculated to be 0.72×10~(-20) cm2 for the Na YF4 single crystal with Ho~(3+) molar percentage of 1% and Pr~(3+) molar percentage of 0.5% according to the measured absorption spectrum.All results suggest that the Ho~(3+)/Pr~(3+) co-doped Na YF4 single crystal may have potential applications in mid-infrared lasers.
The Ho ~ (3 +) / Pr ~ (3+) co-doped Na YF4 single crystals with various Pr ~ (3 +) concentrations and constant Ho ~ (3 +) molar percentage of ~ 1% were grown by an improved Bridgman method. Compared with the Ho ~ (3+) single-doped Na YF4 crystal, an obviously enhanced emission band at 2.85 μm was observed under 640 nm excitation. The Judd-Ofelt strength parameters (? 2,? 4 and? 6) are calculated from the radiative transition probabilities (A), the fluorescence branching ratios (β) and the radiative lifetime (τrad) are obtained in the meantime. energy transfer from Pr ~ (3+) to Ho ~ (3+) and the optimum The emission emission of Ho ~ (3 +) ions around 2.85 μm are investigated. Moreover, the maximum emission cross section of above samples at 2.85 μm is calculated to be 0.72 × 10 ~ (-20) cm2 for the Na YF4 single crystal with Ho (3+) molar percentage of 1% and Pr ~ (3+) molar percentage of 0.5% according to the measured absorption spectrum. All results suggest that the Ho ~ (3 +) / Pr ~ (3+) Na YF4 single crystal may have pot ential applications in mid-infrared lasers.