| 题名 | 稀土离子掺杂的新型中红外激光材料 |
| 作者 | 范金太 |
| 学位类别 | 博士 |
| 答辩日期 | 2012 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 张龙 |
| 关键词 | 中红外激光，稀土掺杂，锗酸盐玻璃，微纳复合 |
| 其他题名 | Novel mid-infrared laser materials doped with rare-earth ions |
| 中文摘要 | 2~3 μm中红外激光在医疗手术、遥感勘测、人眼安全激光雷达、有害气体探测等方面有着重要的应用。研究和开发2~3 μm波段中红外激光增益介质是发展该波段激光的关键。得益于玻璃易于大尺寸制备、可以拉制成光纤、稀土溶解度较高等优点，Tm3+、Ho3+和Er3+离子掺杂的激光玻璃备受关注。 本文以钡镓锗系统锗酸盐玻璃为研究对象，对它进行稀土离子掺杂，通过光谱性质研究和玻璃组成调整，以期制备出在2.0 μm波段有着优秀光谱性质和成玻璃性能良好的激光玻璃并实现2.0 μm波段的激光输出。在此基础上，进一步探索Er3+掺杂的CaF2与氟磷玻璃微纳复合材料的制备，探索了制备工艺对样品中CaF2晶粒形貌和样品透过率的影响，并得到了2.7 μm的荧光。 论文第一章首先介绍了中红外激光的广泛应用以及中红外激光材料激活中心的基础理论——稀土离子光谱学。重点综述了Tm3+和Ho3+掺杂的2.0 μm激光及Er3+掺杂的2.7 μm激光的发展历程和最新研究进展，介绍了适合作为2.0 μm激光的稀土离子掺杂基质玻璃——钡镓锗（BGG）锗酸盐玻璃的结构和性能，提出了Er3+离子掺杂的CaF2纳米晶与氟磷玻璃微纳复合实现Er3+离子2.7 μm高效发光的思想。最后给出了本文工作的研究思路。 论文第二章详细给出了实验中所用到的测试方法、设备及其参数以及理论计算方法。 论文第三章中，我们在BGG三元玻璃的成玻璃区域改变玻璃组成，研究组成改变对玻璃光学性质和对掺杂Tm3+离子光谱参数的影响。结果显示玻璃中BaO和Ga2O3会提高BGG玻璃的折射率，而GeO2则降低玻璃的折射率。Tm3+在BGG玻璃中的J-O强度参数Ω2对玻璃组成改变引起的Tm-O共价性的改变不敏感，Tm3+离子局域结构的变形对Ω2影响较大。此外，我们向BGG中引入BaF2研究了BaF2对OH-根的除去作用。结果表明BaF2能有效地除去BGG玻璃中的OH-，但是BaF2降低了Tm3+的吸收截面和发射截面。Tm3+的各J-O参数也随着玻璃中BaF2含量的增加而减小。 论文第四章中，我们对以BGG玻璃为基础经组分调整和性能优化后的氟锗酸盐（FGe）玻璃进行Tm3+单掺，Yb3+-Tm3+双掺和Yb3+-Ho3+双掺的光谱性质研究。在Tm3+单掺的FGe玻璃中，Tm3+的最佳掺杂浓度为1 mol%，高于此掺杂浓度的样品由于浓度淬灭，荧光光强减弱。FGe玻璃中Tm3+的J-O强度参数为Ω2=5.63×10-20 cm2，Ω4=2.45×10-20 cm2，Ω6=0.75×10-20 cm2，3F4能级的寿命为2.76 ms，受激发射截面为6.8×10-21cm2。以1 mol% Tm2O3掺杂的FGe玻璃为激光增益介质，在最高功率为1W的钛宝石锁模脉冲激光器泵浦下，我们获得了83 mW的激光输出，激光中心波长为1968 nm，半高宽为12.6 nm，激光斜率效率为13.7%。Yb3+-Tm3+双掺的FGe玻璃样品在980 nm LD 激发下于1.8 μm波段有很强的荧光。固定Tm3+含量，荧光强度随Yb3+离子浓度的增加先增大后减小。Yb3+-Tm3+双掺的FGe玻璃样品在980 nm LD激发下有很强的上转换发光，双转化发光强度随Yb3+离子浓度的变化关系与1.8 μm荧光的变化关系一致。计算了Yb3+-Tm3+之间的微观能量传递系数CYb-Tm=8.55×10-40cm6s-1，能量传递效率为54.3%。在Yb3+-Ho3+的样品中，980 nm LD 激发下，样品在2.0 μm处有较强的荧光，荧光光强随Yb3+浓度增加而不断增强。双掺样品在980 nm LD 激发下还显现出很强的双转化荧光，上转换均为双光子过程。计算了Ho3+离子在双掺的FGe玻璃中的各项荧光参数，包括J-O强度参数、自发辐射几率、荧光寿命、荧光分支比，受激发射截面等。Yb3+-Ho3+之间的微观能量传递系数CYb-Ho=2.22×10-40 cm6s-1，能量传递效率为87%。 论文第五章详细介绍了CaF2/FP晶体玻璃透明复合材料的制备思路，通过改变氟磷玻璃中磷酸盐组分的含量制备了折射率与CaF2相匹配的FP玻璃。探索了FP玻璃粉体微观形貌与球磨时间的关系，研究了不同CaF2/FP比值的初始混合粉末在不用温度下热处理后样品的XRD和透过率。在热处理过程中，CaF2会熔于FP玻璃，热处理温度越高，熔入量越大。FP玻璃熔解CaF2的极限约为两者总和的20 wt%。CaF2初始含量低于该值的复合样品在高于820℃的温度处理下，CaF2全部熔解且在冷却过程中不重新析出；CaF2初始含量高于该值，即使在高温下全部熔解，在冷却过程中还会重新析出。较高温度处理后的样品在冷却过程中，CaF2重新析出时倾向于形成雪花状的枝晶，并使复合样品失透。最终，我们确定了30CaF2-70FP初始混合粉末在820℃热处理1小时的复合样品制备工艺。 在论文第六章，我们采用共沉淀法制备了Er3+CaF2纳米晶粉体，并将它与FP玻璃复合获得透明的Er3+CaF2/FP晶体玻璃微纳复合材料。复合样品的XRD图谱证实了热处理后样品中CaF2的存在。样品断面的微观相貌和EDS能谱分析显示Er3+：CaF2均匀分散与玻璃基质中，Er3+：CaF2大小约为10 μm。复合样品在红外的透过率为80%，可见波段透过率为60%~80%。样品在980 nm LD 激发下有很强的2.7 μm荧光。改变CaF2中Er3+离子的掺杂浓度，发现Er3+离子掺杂量高于10 mol% Er3+：CaF2的复合样品中没有CaF2微晶却存在ErPO4晶体，样品完全失透。 最后一章对全文的实验结果进行了总结并指出了存在的不足和需要改进的地方。 |
| 英文摘要 | Mid-infrared lasers of the wavelength ranging from 2 to 3 μm have many potential applications including medical surgery, remote sensing, eye-safe lidar, toxic gas detecting, etc. The research of laser material is essential to the development of the infrared laser working within this wavelength. Rare earth ions doped laser glass has been paid great attention because glass is relatively easy to produce into large size, can be drawn into fiber and has high solubility of rare earth ions. The work in this thesis can be divided into two sections. In the first section, the spectroscopic properties of rare earth ions doped barium gallate germanate (BGG) glass was studied, based on which the compositions of the glass were modifed to obtain laser glass that has good glass-forming ability with excellent spectroscopic and laser properties near 2.0 μm. In the second section, as a further study, the preparation and spectroscopic properties at 2.7 μm of a novel Er3+ ions doped crystal/glass micro-composite were explored. The wide-range applications of mid-infrared lasers were described in the first chapter. The spectroscopy of rare earth ions which are the active centers of infrared laser material was introduced. The history and recent progress of Tm3+, Ho3+ and Er3+ ions doped laser glass and laser crystals were reviewed. The structure and properties of BGG glass were also introduced, which was followed by the idea of crystal/glass micro-composite. At the end of this chapter, the approch of the work was presented. In the second chapter, the specific measurement and theories were listed. In chapter III, the compositional dependence of optical and spectroscopic properties of Tm3+ doped BGG glass was investigated. The results showed that the ingredients of BaO and Ga2O3 increase the refractive index of BGG glass while GeO2 has the opposite effect. The J-O intensity parameter of Ω2 is insensitive to the change of of the covalency of Tm-O band tthat is caused by compositional variation in the glass forming area. In contrast, the local structural distortion around Tm3+ ions in the glass has larger effect on Ω2. The introduction of BaF2 into the BGG glass eliminates OH- groups efficiently, however, decreases the J-O parameters, absoption cross section and emission cross section of Tm3+. In chapter IV, the spectroscopic properties of Tm3+ doped, Yb3+-Tm3+ doped, and Yb3+-Ho3+ doped fluorogermanate (FGe) glass that was developed from BGG glass were studied. The optimum doping level of Tm2O3 in the FGe glass was found to be 1 mol%. FGe glass doped with more the 1 mol% of Tm2O3 undergoes concentration quenching. The J-O paremeters of Tm3+ in FGe glass are Ω2=5.63×10-20 cm2, Ω4=2.45×10-20 cm2, Ω6=0.75×10-20 cm2, respectively. The radiative lifetime of 3F4 manifold was calculated to be 2.76 ms. The emission cross section is 6.8×10-21cm2. 83 mW laser action was observed in 1 mol% Tm2O3 doped FGe glass. The pump source was a pulsed mode-lock Ti-saphire laser working at 790nm with a maxium power of 1W. The wavelength of the observed laser centered at 1968 nm. The FWHM of the laser was 12.6 nm. The slope efficiency was 13.7%. In Yb3+-Tm3+ doped FGe glass, strong fluorescence near 1.8 μm was observed when excited by a 980 nm LD. The fluorescence intensity increased and then decrease as the Yb3+ concentration increased and maintained the doping level of Tm3+. Yb3+-Tm3+ doped FGe glass exhited strong up-conversion emission under 980 nm excitation. The relation between up-converion intensity and Yb3+ concentration was the same as that between 1.8 μm intensity and Yb3+ concentration. The micro-parameter of the energy transfer from Yb3+ to Tm3+ was calculated to be 8.55×10-40cm6s-1, and energy transfer efficiency 54.3%. The Yb3+-Ho3+ codope FGe showed strong emission around 2.0 μm under 980 nm excitation. The intensity increased along with Yb3+ increasing while kept the Ho3+ concentration constant. Up-conversion luminescence was also observed in the codoped samples under the same excitation. The calculation showed the up-conversions were 2 phonons process. The J-O parameters, spontaneous radiative emission, branch ratio and stimulated emission cross section were calculated. The micro-parameter of energy transfer from Yb3+ to Ho3+ was 2.22×10-40 cm6s-1. The energy transfer efficiency was 87%. Chaper V presented the detailed idea and preparation process of Er3+ doped CaF2/FP micro-composite. The refractive index of the FP glass was adjusted to match that of CaF2 crystal by varying the content of phosphate ingredient of the glass. The dependence of the glass particle size on the ball-milling duration was investigated. The XRD patterns and transmittance spectra of the obtained samples that had different initial weight ratio of CaF2 powder to FP glass powder and were processed at different temperature were measured. The results indicated that CaF2 dissolved into FP glass liquid when the powder mixture was heat treated. The higher treating temperature, the more CaF2 dissolved. The solubility of CaF2 in FP at room temperature was estimated to 20%. The samples with initial CaF¬2 weight percent less than 20% were totally glassy. In contrast, in the samples with more initial CaF2 content than 20%, CaF2 precipitated when the heat treating process ended and the temperature dropped down, even though CaF2 had been completely dissolved in FP glass liquid during heat-treating process. The optimized parameters for preparation of the CaF2/FP micro-composite were set as: 30 wt% CaF2 – 70 wt% FP as intitial powder mixture heat treated at 820 ℃ for 1 hour. In the chapter VI, Er3+ doped CaF2/FP micro-composites were produce. The Er3+ doped CaF2 particles were synthesized with co-precipitating method. The XRD patterns of the samples verify the existence of CaF2. The SEM pictures and EDS analysis revealed Er3+:CaF2 crystal particles dispersed homogeneously in FP glass and the CaF2 particles were ~10 μm in size. The composites were transparent. The transmittance was 80% in infrared wavelength range and 60%~80% in visable wavelength range. The composites had stong emission around 2.7 μm under 980 nm excitation. The attempt to increase Er3+ doping level in CaF2 showed that 30 wt% Er3+:CaF2-70 wt% FP with CaF2 doped more than 10 mol% of ErF3 resulted in totally opaque after heat treatment due to the precipitation of ErPO4 as revealed by the XRD patterns. The last chapter summarized our work and concluded what should be done for further research. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15680]  |
| 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 | 范金太. 稀土离子掺杂的新型中红外激光材料[D]. 中国科学院上海光学精密机械研究所. 2012. |
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