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题名	稀土离子掺杂的LaF3晶体的生长及性能研究
作者	洪佳琪
文献子类	博士
导师	杭寅
关键词	激光晶体 Laser crystal LaF3晶体 LaF3 crystal 稀土掺杂 Rare earth doping 晶体生长 Crystal growth 光谱性能 Spectral performances
其他题名	Study of growth, spectra and laser properties on Re3+ doped LaF3 crystal
英文摘要	氟化物晶体是重要的激光基质材料之一，与氧化物基质晶体相比，氟化物晶体普遍具有：较宽的透光范围和较高的透过率，可以实现较长波段的激光输出；较低的声子能量，降低无辐射跃迁几率，从而提高掺杂离子的发光量子效率并延长其能级寿命从而有利于储能；较低的折射率可限制强光泵浦下的非线性效应；较低的熔点利于晶体生长。探索新型氟化物激光晶体，对实现新型高效的小型化全固态中小功率激光器具有重要意义，也是目前激光领域的研究热点之一。LaF3晶体具有如下优点：晶体声子能量低，只有350 cm-1，作为激光基质材料可降低无辐射跃迁几率；晶体禁带宽度较宽，对应的紫外透光范围低至＜200 nm，可实现深紫外波段的激光输出；由于La本身属镧系元素，离子价态+3，因而在三价稀土离子掺杂的过程中不存在电价不平衡的问题；LaF3属于单轴晶体，作为激光基质材料可以直接输出偏振激光。虽然LaF3晶体具有优良的综合性能，但是目前国内外对稀土离子掺杂的LaF3晶体研究还很少，已经报道的稀土掺杂LaF3晶体的光谱性质也不够详细系统。本论文基于以上研究现状，选取Nd3+、Ho3+以及Yb3+掺杂的LaF3晶体为研究对象，主要研究了掺杂后的Nd3+:LaF3晶体、Ho3+:LaF3晶体以及Yb3+:LaF3晶体的结构、热学、光谱、激光等性能。主要研究内容及结论包括以下几个方面： 1. 使用提拉法生长了掺杂浓度为1.5 at.% 的Nd:LaF3晶体，晶体尺寸约φ30×65 mm3，晶体光学质量良好。研究了该晶体的结构、Nd3+的分凝系数以及晶体在300-575 K的热导率。根据J-O理论，拟合了该晶体的晶体场参数Ω2,4,6并计算了部分光谱参数。测试了该晶体的光谱性能：在793 nm处的最大吸收截面为1.89×10-20 cm2，FWHM约19 nm；~0.9 μm波段荧光分支比显示其高效激光输出可能；~1.06 μm波段荧光光谱显示其多波长输出可能性，其中在1040、1047及1064 nm处的发射截面分别为1.49×10-20、1.73×10-20及2.09×10-20 cm2；荧光衰减曲线呈一次指数关系，4F3/2能级荧光寿命拟合得522 μs。使用该晶体首次获得了连续双波长激光输出：激光峰值分别为1040 nm和1065 nm；激光阈值为0.07 W；光光效率为16.8%；斜率效率为18.5%；当泵浦光为1.8 W时，得到最大激光输出为302 mW。 2. 使用温梯法生长了掺杂浓度为1.5 at.% 的Ho:LaF3晶体，晶体光学质量良好，尺寸约φ30×35 mm3，Ho3+的分凝系数约0.62。测试并计算了该晶体的光谱性能：在1962 nm处的最大吸收截面为0.24×10-20 cm2，FWHM约110 nm；根据拟合的J-O参数Ω2,4,6得到5I6→5I7跃迁对应的~2.9 μm处的荧光分支比达到约35%；晶体2 μm波段最强荧光峰位于1930 nm，发射截面0.39×10-20 cm2；2.9 μm波段荧光带平滑并且比较宽，FWHM 宽达115 nm，最大荧光发射截面0.63×10-20 cm2；室温下Ho:5I7能级荧光寿命为25.81 ms；Ho:5I6能级荧光寿命为10.37 ms。 3. 采用温梯法首次生长了共掺0.5 at.% Pr的Ho:Pr:LaF3晶体，对比研究了Ho:Pr:LaF3晶体与Ho:LaF3晶体在2 μm以及2.9 μm波段的荧光特性：共掺Pr后，2 μm波段的荧光强度显著减弱，而2.9 μm波段的荧光略有增强；共掺Pr后，Ho:5I7能级的荧光寿命迅速变短，而Ho:5I6能级的荧光寿命变化不大；表明共掺Pr3+的退敏化效果很明显，有利于2.9 μm波段的激光输出。计算了Ho3+-Pr3+之间的能量传递效率：Ho3+:5I6→Pr3+:3F4以及Ho3+:5I7→Pr3+:3F2+3H6的能量传递效率分别为28%和71%。研究结果表明Ho:Pr:LaF3晶体是一种有潜力的2.9 μm激光材料。 4. 使用温梯法生长了掺杂浓度为5 at.%的Yb:LaF3晶体，尺寸约φ30×35 mm3，Yb3+的分凝系数约为0.26。测试了Yb:LaF3晶体a轴和c轴的热导率。测试了该晶体的光谱性能：室温吸收光谱及荧光光谱均呈宽带分布，其中吸收光谱FWHM大于60 nm，荧光光谱FWHM约50 nm；在974 nm处的最大吸收截面为0.24×10-20 cm2，在994 nm处的最大发射截面为0.47×10-20 cm2；晶体Yb:2F5/2能级荧光寿命拟合得2.92 ms。计算了Yb:LaF3晶体的激光参数：在最大吸收截面974 nm处，泵浦饱和功率密度Isat为29.1 kWcm-2；在荧光峰值1009 nm处，最小泵浦功率密度Imin为0.851 kWcm-2。; Fluoride crystals are important laser matrix materials and have several advantages when compared to oxides: higher transparency in a wider range to achieve longer wavelength laser output; lower phonon-energy to reduces non-radiative relaxation and improve the quantum efficiency of the dopant ions, which extend the lifetime of the ions and facilitate energy storage; lower refractive index to limit the non-linear effect with strong pumping; lower melting point to favor crystal growth. Exploring new fluoride laser crystals is of great significance to realize new and efficient miniaturized all solid-state lasers, and it is also one of the hotspots in the field of lasers. LaF3 crystal has the following advantages: a low phonon energy of only 350 cm-1, which can reduce the probability of non-radiation transition; a wide crystal band gap width and the corresponding UV transmission range as low as <200 nm, which can realize laser output in the dark ultraviolet range; a lanthanide element of La, ion valence +3, so that there is no problem of price imbalance in the process of trivalent rare earth ion doping; a uniaxial crystal, which can directly output polarized lasers. Although LaF3 crystal has excellent comprehensive properties, there is few studies on rare earth doped LaF3 crystals as laser materials. Based on the above research situation, in this thesis, we investigated the growth, structure, thermal, spectra and laser performance of Nd3+, Ho3+ and Yb3+ doped LaF3 crystals. The main research contents are as follows: 1. The 1.5 at.% Nd-doped LaF3 crystal of about φ30 × 65 mm3 with high optical quality was grown successfully by the Czochralski method. The crystal structure, the separation coefficient of Nd3+and the thermal conductivity at 300 - 575 K were studied. Several spectral parameters are calculated according to the J-O theory and the crystal field parameters Ω2,4,6. The spectral performances were measured: the maximum absorption cross section at 793 nm is 1.89×10-20 cm2 with FWHM of 19 nm; the emission cross section at 1040, 1047 and 1064 nm are 1.49×10-20, 1.73×10-20and 2.09×10-20 cm2, which showed multi-wavelength output probability; the fluorescence decay curve was exponential, and the fluorescence lifetime of4F3/2 was 522 μs. Continuous dual-wavelength laser output was realized at 1040 nm and 1065 nm, the laser threshold was 0.07 W, The optical-optical conversion efficiency was 16.8%, the slope efficiency was 18.5%, and maximum laser output was 302 mW with 1.8 W pumping. 2. The 1.5 at.% Ho-doped LaF3 crystal of about φ30 × 35 mm3 with high optical quality was grown successfully by the TGT method. The spectral performances were measured: the maximum absorption cross section at 1962 nm was 0.24×10-20 cm2 with FWHM of 110 nm; the fluorescence branching ratio at ~ 2.9 μm corresponding to the 5I6→5I7 transition was about 35%; the strongest fluorescence peak of ~ 2 μm band was at 1930 nm with emission cross section of 0.39×10-20 cm2,the fluorescence band of ~ 2.9 μm band was smooth and wide, where the FWHM was 115 nm and the maximum emission cross section was 0.63×10-20 cm2; the fluorescence lifetime of Ho:5I7and Ho:5I6were 25.81 msand 10.37 ms, respectively. 3. The 0.5 at.% Pr-co-doped Ho:Pr:LaF3crystal was grown successfully by the TGT method. The fluorescence properties in the 2 μm and 2.9 μm bands of Ho:LaF3crystal and Ho:Pr:LaF3crystal were studied: with Pr-co-doping, the fluorescence intensity of the 2 μm band was significantly weakened while that of 2.9 μm band was slightly enhanced; the fluorescence lifetime of Ho:5I7 was immediately shortened and that of Ho:5I6 was not much changed. The results showed that the deactivation effect of Pr3+ to Ho3+ was obvious, which was beneficial to the laser output of 2.9 μm band. The energy transfer efficiency between Ho3+ and Pr3+ was calculated: 28%and 71%for Ho3+:5I6 → Pr3+:3F4and Ho3+:5I7 → Pr3+:3F2+3H6, respectively. 4. The 5 at.% Yb-doped LaF3 crystal of about φ30 × 35 mm3 was grown successfully by the TGT method, and the separation coefficient of Yb3+ was about 0.26. The crystal thermal conductivity at 300 - 575 K along both a-axis and c-axis were studied. The spectral performances were measured: the maximum absorption cross section at 974 nm was 0.24×10-20 cm2 with FWHM of about 60 nm; the maximum emission cross section at 994 nm was 0.47×10-20 cm2 with FWHM of 50 nm; the fluorescence lifetime of Yb:2F5/2 was 2.92 ms. Several laser parameters were calculated: the pump saturation power density was 29.1 kWcm-2at absorption peak 974 nm; the minimum pump power density was 0.851 kWcm-2at emission peak 1009 nm.
学科主题	材料学
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/31011]
专题	中国科学院上海光学精密机械研究所
作者单位	中国科学院上海光学精密机械研究所
推荐引用方式 GB/T 7714	洪佳琪. 稀土离子掺杂的LaF3晶体的生长及性能研究[D].

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