Enhanced emission at 2.85 μm of Ho3+/Pr3+ co-doped α-NaYF4 single crystal

The Ho³⁺/Pr³⁺ co-doped NaYF₄ single crystals with various Pr³⁺ concentrations and constant Ho³⁺ molar percentage of ~1% were grown by an improved Bridgman method. Compared with the Ho³⁺ single-doped NaYF₄ crystal, an obviously enhanced emission band at 2.85 μm is observed under 640 nm excitation. The Judd-Ofelt strength parameters (Ω ₂, Ω ₄ and Ω ₆) are calculated, the radiative transition probabilities (A), the fluorescence branching ratios (β) and the radiative lifetime (τ _rad) are obtained in the meantime. The energy transfer from Pr³⁺ to Ho³⁺ and the optimum fluorescence emission of Ho³⁺ 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 NaYF4 single crystal with Ho³⁺ molar percentage of 1% and Pr³⁺ molar percentage of 0.5% according to the measured absorption spectrum. All results suggest that the Ho³⁺/Pr³⁺ co-doped NaYF₄ single crystal may have potential applications in mid-infrared lasers.     

Tm~(3+)掺杂Na_5Lu_9F_(32)单晶体的1.8μm优化发射性能研究（英文）

采用改进过的布里奇曼法成功地生长了Tm~(3+)离子浓度从0.5~4mol%变化的高质量Na_5Lu_9F_(32)单晶.在790nm LD激发下,研究了不同Tm~(3+)掺杂晶体在1.86μm波段的荧光发射性能、衰减曲线以及Tm~(3+)离子之间的能量传递过程.当Tm~(3+)离子掺杂浓度增加到~1.95mol%时,晶体在1.86μm处的荧光发射强度达到最大.然后,随着Tm~(3+)离子浓度进一步的增大,发射强度迅速下降.然而,Tm~(3+)离子在3F4能级处的荧光寿命随着Tm~(3+)掺杂浓度从0.5增加到4mol%,逐渐降低.同时计算了1.86μm处最大的受激发射截面为0.80×10~(-20) cm~2.Tm~(3+)离子的浓度猝灭效应和离子之间的交叉弛豫能量传递过程是造成1.86μm荧光发射变化的主要原因.     

The optical properties of Tm3+ doped Na5Lu9F32 single crystal

Tm3+ doped Na5Lu9F32 single crystal with high optical quality was grown by an improved Bridgman method. The Judd-Ofelt intensity parameters Ωt (t=2, 4, 6) were calculated according to the measured absorption spectra and physical-chemical properties of the obtained Na5Lu9F32 single crystal. The stimulated emission cross-section of the 3F4→3H6 transition (~1.8 μm) is 0.35×10-20 cm2 for Tm3+ doped Na5Lu9F32 single crystal. The emission spectra under the excitation of 790 nm laser diode (LD) and fluorescence lifetime at 1.8 μm were measured to reveal the fluorescence properties of Tm3+ doped Na5Lu9F32 single crystal. The research results show that the Tm3+ doped Na5Lu9F32 single crystal has larger stimulated emission cross-section compared with other crystals. All these spectral properties suggest that this kind of Tm3+doped Na5Lu9F32 crystal with high physical-chemical stability and high-efficiency emission at 1.8 μm may be used as potential laser materials for optical devices.     

HO3+/Tm3+共掺α-NaYF4单晶体的光谱特性

采用坩埚下降法生长出Ho3+离子掺杂浓度～1.90 mol％、Tm3+不同掺杂离子浓度(0.99 mol％,1.58 mol％,2.37 mol％,3.16 mol％,3.99 mol％,7.19 mol％)的双掺杂立方晶相NaYF4单晶体.根据测定的吸收光谱以及800 nmLD波长激发下的发射光谱、发射截面和衰减曲线,研究从Tm3+离子到Ho3+离子的能量传递机制、Tm3+离子的浓度猝灭效应和Ho3+离子在2.04 μm波段的优化发光效应.当Ho3+离子浓度保持为～1.90 mol％不变,Tm3+离子浓度从0.99 mol％增加到1.59 mol％时,2.04 μm波段的发射强度逐步增强;当浓度从1.59mol％增加到7.19mol％时,发射强度逐步减弱.Ho3+ (1.90 mol％)/Tm3+ (1.59 mol％)共掺的单晶体的发射截面最大,达到2.17×10-20 cm2,其荧光寿命最长,为21.72 ms;同时,根据Ho3+离子的吸收截面和Tm3+离子的发射截面,计算得到该样品从Tm3+:3F4→Ho3+:5I7稀土离子能量传递系数和Ho3+:5I7→Tm3+:3F4反传递系数分别为CTm-Ho=24.14×10-40 cm6/s,CHo-Tm=2.05×10-40 cm6/s.