新型稀土离子掺杂氟化铅中红外激光晶体的研究
文献类型：学位论文
| 作者 | 张沛雄 |
| 学位类别 | 博士 |
| 答辩日期 | 2016 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 杭寅 |
| 关键词 | 氟化物激光晶体，2-3?m中红外激光晶体，晶体生长，光谱性能 |
| 其他题名 | Novel rare earth ions doped lead fluoride mid-infrared laser crystals |
| 中文摘要 | 中红外激光（2～5 μm）在军事、医疗、光谱学、环境监测、自由空间激光通信等领域均有重要的应用，也是目前激光器领域的研究热点。而激光增益介质材料是中红外激光器的核心部分，然而目前具有激光效率高的中红外激光材料还处于探索阶段，因此研发新型高效的中红外激光材料，对于发展中红外激光器及其应用具有重要意义。氟化铅晶体由于具有声子能量低、红外透过高、物理化学性能稳定等特点，特别适合作为中红外固体激光器理想的基质材料。基于以上认识和目的，本论文研究了新型2～3 μm中红外稀土离子掺杂氟化铅激光晶体的生长和光学性能，从而为获得新型2～3 μm固体激光材料提供一定的理论基础和实验基础。 本论文包括六章，前面两章分别是文献综述和实验方法及理论计算基础；第三章到第五章是本论文的核心部分；最后一章第六章是对本论文的总结以及展望。 本论文的核心内容主要包括以下几个方面的研究： 1. Ho3+:PbF2晶体和Ho3+/Yb3+:PbF2晶体，以及Dy3+:PbF2晶体和Dy3+/Yb3+:PbF2晶体的生长工艺研究。系统研究了利用坩埚下降法生长Dy3+，Ho3+，Yb3+掺杂PbF2晶体过程中的生长条件和参数，包括温度梯度的选择，生长速度的确定，生长环境中的除氧处理，除氧剂的选择，坩埚材料及形状的选择等工艺参数，最后掌握了稀土离子掺杂PbF2晶体的相关生长工艺。 2. Ho3+:PbF2晶体和Ho3+/Yb3+:PbF2晶体，以及Dy3+:PbF2晶体和Dy3+/Yb3+:PbF2晶体热学性能的研究，包括晶体的密度，比热，热扩散系数以及热导率等参数。 3. Ho3+:PbF2晶体和Ho3+/Yb3+:PbF2晶体的光学性能研究。结果表明：Ho3+:PbF2晶体和Ho3+/Yb3+:PbF2晶体具有低的声子能量，分别为257 cm-1和255 cm-1；红外透过率高，从2.8 ?m至9 ?m的透过率都在83 %以上；根据J-O理论计算了Ho3+离子在晶体PbF2晶体的中强度参数Ω2，4，6及振子强度fJ,J'、自发辐射跃迁几率AJ,J'、辐射寿命?rad和荧光分支比?J等光学参数；得出Ho3+:PbF2晶体和Ho3+/Yb3+:PbF2晶体在3 ?m 波段的荧光分支比高达20.99%和20.52%；在3 ?m 波段都有强的荧光发射，特别是Yb3+离子的掺入，明显地增强了此波段的荧光强度；Ho3+:PbF2晶体和Ho3+/Yb3+:PbF2晶体在3 ?m 波段的荧光寿命分别为6.11 ms和5.79 ms，在2 ?m 波段的荧光寿命分别为13.6 ms和10.8 ms；Yb3+离子的共掺，可以发生从Yb3+-2F5/2能级到Ho3+-5I6能级的能量传递比较明显，提供了一条有效的泵浦通道，能够解决单掺Ho3+离子缺乏合适泵浦源和泵浦效率低的问题；Ho3+-Yb3+之间的能量传递效率为96.7%，表明Yb3+离子确实是一个有效的敏化离子。 4. Dy3+:PbF2晶体和Dy3+/Yb3+:PbF2晶体的光学性能研究。结果表明：Dy3+:PbF2晶体和Dy3+/Yb3+:PbF2晶体具有低的声子能量，分别为250 cm-1和251 cm-1；红外透过率高，从2.8 ?m至9 ?m的透过率都在80 %以上；根据J-O理论计算了Ho3+离子在晶体PbF2晶体的中强度参数Ω2，4，6及振子强度fJ,J'、自发辐射跃迁几率AJ,J'、辐射寿命?rad和荧光分支比?J等光学参数；得出Dy3+:PbF2晶体和Dy3+/Yb3+:PbF2晶体在3 ?m 波段的自发辐射几率高达61.1 s-1和61.9 s-1；在3 ?m 波段都有强的荧光发射，即使是Yb3+离子的掺入，对此波段的荧光强度影响不大；Dy3+:PbF2晶体和Dy3+/Yb3+:PbF2晶体在3 ?m 波段的荧光寿命分别为15.3 ms和15.4 ms，发光量子效率高达93.3%和95.0%；Yb3+离子的共掺，可以发生从Yb3+-2F5/2能级到Dy3+-5I6能级的能量传递比较明显，提供了一条有效的泵浦通道，能够解决单掺Dy3+离子缺乏合适泵浦源和泵浦效率低的问题；得出Dy3+-Yb3+之间的能量传递效率为97.7%，表明Yb3+离子确实是一个有效的敏化离子。 |
| 英文摘要 | Owing to the strong absorption of radiation by water and hydroxyapatite at near 2-5 μm region, mid-IR (MIR) lasers operating around 2-3 μm have attracted much attention in view of the possible applications in medical and sensing technologies. It can also be served as ef?cient and high quality laser pump sources for longer-wavelength mid-IR oscillators, such as mid-IR optical parametric oscillators (OPO) and THz local oscillators. The laser materials are core parts of the MIR laser. However, up to now, effective MIR laser materials have been rarely actually applied. Therefore, it is important to research new and highly efficient MIR laser materials for the application of MIR laser. In order to get powerful 3 μm MIR emission, the ideal host material is expected to possess low phonon energy suppressing nonradiative relaxation between adjacent energy levels, minimal absorption coef?cient in the H2O absorption band at around 3 μm with no effect to the 3 μm emission, and high radiative emission rates improving laser emission ef?ciency. In our work, we have focused our attentions on a new potential gain medium β–PbF2 crystal, due to its combination of good thermal properties, moderate mechanical properties, excellent solubility for rare-earth ions, and high transparency in a wide wavelength range. Moreover, PbF2 crystal has the advantage of being characterized by signi?cantly lower phonon energy, which is bene?cial for suppressing multiphonon de-excitation processes. These characteristics render PbF2 crystal as extremely suitable to be used as a host to mid-IR solid–state lasers. This paper aims to investigate the spectroscopic properties around 2-3 μm emission of rare earth ions (Ho3+ and Dy3+) doped PbF2 crystal that is suitable for 2-3 μm lasers crystal materials and to provide theoretical basis and experimental evidence for 2-3 μm lasers materials. This paper includes the following six chapters. The first two chapters are the literature review, experimental methods and theoretical basis. The middle three chapters are core parts of the paper. The last chapter is the conclusion and outlook. The core parts of the paper include the following four sections: 1. Section one: the research of growth technology of Ho3+:PbF2, Ho3+/Yb3+:PbF2, Dy3+:PbF2, and Dy3+/Yb3+:PbF2 crystals. The growth conditions and parameters of the growth of Ho3+, Yb3+, Dy3+ doped PbF2 crystals by the Bridgman technique have been systematically researched, including to the choice of temperature gradient, the select of growth rate, the oxide-eliminating of growing environment, the choice of deoxidant, the selection of the material and form of crucible, and so on. At last, we have mastered the growth technology of rare earth ions doped PbF2 crystal, Specific content as follows. 2. Section two: the research of thermal properties of Ho3+:PbF2, Ho3+/Yb3+:PbF2, Dy3+:PbF2, and Dy3+/Yb3+:PbF2 crystals, including to the density, specific heat, thermal diffusivity, and thermal conductivity. 3. Section three: the research of spectroscopic properties of Ho3+:PbF2, and Ho3+/Yb3+:PbF2 crystals. The results are as following: the phonon energy of Ho3+:PbF2, and Ho3+/Yb3+:PbF2 crystals are as low as 257 cm-1and 255 cm-1, respectively；good IR transmittance around 3 μm and extends up to 9 μm (about 83 %); the J-O intensity parameters Ω2,4,6, oscillator strength, spontaneous emission probabilities, fluorescence branching ratios, and radiative lifetime of Ho3+ ions in the crystals have been calculated, and the results showed that an intense 2.8 μm emission in Ho:PbF2 crystal was observed, and an enhanced emission at 2.86 μm in Ho3+/Yb3+:PbF2 crystal was observed from the crystal under excitation of a common 970 nm laser diode for the ?rst time. 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. In comparison to Ho:PbF2 crystal, the Ho3+/Yb3+:PbF2 crystal possessed comparable quantum ef?ciency (88.8%), and ?uorescence branching ratio (20.52%) along with a larger calculated emission cross section (1.90×10?20 cm2) corresponding to the laser transition 5I6→5I7 of Ho3+. It was found that the introduced Yb3+ enhanced the 2.86 μm emission by depopulating the Ho3+:5I7 level. The energy transfer (ET) ef?ciency from Yb3+:2F5/2 to Ho3+:5I6 is as high as 96.7%, indicating that Yb3+ ion is an effective sensitizer for Ho3+ ion in PbF2 crystal. These results suggest that the Ho:PbF2 crystal may be a promising material for 2.8 μm laser applications, and Ho3+/Yb3+:PbF2 crystal may become an attractive host for developing solid state lasers at around 2.86 μm under a conventional 970 nm LD pump. 4. Section four: the research of spectroscopic properties of Dy3+:PbF2, and Dy3+/Yb3+:PbF2 crystals. The results are as following: the phonon energy of Dy3+:PbF2, and Dy3+/Yb3+:PbF2 crystals are as low as 250 cm-1and 251 cm-1, respectively；good IR transmittance around 2.8 μm and extends up to 9 μm (about 80 %); the J-O intensity parameters Ω2,4,6, oscillator strength, spontaneous emission probabilities, fluorescence branching ratios, and radiative lifetime of Ho3+ ions in the crystals have been calculated, and the results showed that ef?cient emission at around 3 μm from the crystal was observed under excitation of a conventional 970 nm laser diode (LD). The Dy:PbF2 crystal has long ?uorescence lifetime (15.3 ms), large emission cross section (1.30×10?20 cm2), and high quantum efficiency (93.3 %) corresponding to the stimulated emission of Dy3+:6H13/2→6H15/2 transition. In comparison to Dy:PbF2 crystal, the Dy3+/Yb3+:PbF2 crystal possesses long ?uorescence lifetime 15.4 ms, high quantum ef?ciency 95.0 %, and large emission cross section 1.37×10?20 cm2 corresponding to the stimulated emission of Dy3+:6H13/2→6H15/2 transition. It was demonstrated that the energy transfer ef?ciency from Yb3+ to Dy3+ is as high as 97.7%, con?rms that the Yb3+ ion can be used as an effective sensitizer for Dy3+ ion. These results suggest that the Dy:PbF2 crystal may be a promising material for 3 μm laser applications, and the Dy3+/Yb3+:PbF2 crystal is a promising material for 3 μm laser applications under being pumped by a conventional 970 nm LD. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15971]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 张沛雄. 新型稀土离子掺杂氟化铅中红外激光晶体的研究[D]. 中国科学院上海光学精密机械研究所. 2016. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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