| 题名 | 掺稀土碲酸盐、锗酸盐玻璃与光纤2~3μm光谱和激光性能 |
| 作者 | 范小康 |
| 学位类别 | 博士 |
| 答辩日期 | 2015 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 胡丽丽 |
| 关键词 | 碲酸盐玻璃 锗酸盐玻璃 稀土离子掺杂 2~3μm发光 光纤激光 |
| 其他题名 | Spectroscopic and laser properties of 2~3 μm emissions in rare earth doped tellurite and germanate glasses and fibers |
| 中文摘要 | 近年来，2~3 μm波段中红外固体激光器因在医疗、环境监测和国防等领域有重要应用而受到广泛关注。高性能激光材料作为激光器及激光技术发展的基石，具有重大的研究意义。本论文以研发适用于2~3 μm波段激光光纤为目的，对稀土离子掺杂碲酸盐和锗酸盐玻璃及光纤的物理性质、光谱性质和激光性能进行了研究和分析。 本论文共包括六章，第一章是文献综述，第二章是实验方法和相关理论，第三章到第五章是论文的实验研究和分析，也是本文的核心内容，第六章是结论。 文献综述首先简要介绍了激光及光纤激光器的基本原理、构成及应用。其次，总结了2~3 μm波段激光的应用和产生方式；最后综述了各种稀土掺杂玻璃光纤在2~3 μm波段激光的研究进展和现状，进而提出了本文的研究内容和思路。 论文第二章介绍了玻璃样品及光纤的制备方法和性能表征所用到的测试方法，概述了分析和处理实验数据所需的光谱理论。 论文的第三章分别对Er3+单掺和Er3+/Pr3+共掺在碲酸盐玻璃中的2.7 μm光谱性质进行了计算和分析。研究了在980 nm LD泵浦下，不同掺杂浓度下Er3+离子2.7 μm 波段的荧光强度变化。随着Er2O3浓度从0.1 mol%增加到3 mol%，2.7 μm波段的荧光强度逐渐增强。当掺杂浓度达到3 mol%时，样品的DSC曲线上未出现析晶峰，玻璃表现出良好的热稳定性。利用Judd-Ofelt理论计算得到Er3+离子在2.7 μm波段的自发辐射几率和荧光分支比分别为57.8 s-1和17.3%，峰值受激发射截面位于2708 nm处，为1.12×10-20 cm2。基于上述结果，进一步研究了Er3+/Pr3+共掺碲酸盐玻璃的光谱性能和能量转移机理。从实验结果观察到，少量Pr3+离子即可显著加快4I13/2能级衰减速率，降低该能级的粒子数，同时显著削弱上转换荧光，但对2.7 μm波段荧光强度影响较小。因此，Er3+/Pr3+共掺是一种有效实现Er3+离子粒子数反转的途径，但应优化Pr3+和Er3+离子的浓度和比例。 论文的第四章设计并制备了掺铥锗酸盐玻璃和光纤，并对其2 μm光谱性质和激光性能进行了测试和分析。掺铥锗酸盐玻璃和光纤实验以锗铅玻璃为基质，首先研究了不同Tm3+离子浓度下的2 μm荧光光谱性质和3F4能级的衰减特性，当Tm3+离子掺杂浓度为3×1020 cm-3时，2 μm处的荧光强度最大，3F4能级测试寿命为1.5 ms，量子效率达到45.5%。其峰值受激发射截面位于1864 nm处，为6.15×10-21 cm2；制备了Tm2O3掺杂浓度为2 wt%的锗酸盐单包层多模光纤，测试背景损耗为3.12 dB/m。在793 nm半导体多模激光器和1590 nm光纤激光器泵浦下实现了激光输出，最大输出功率分别为95 mW和44.7 mW，斜率效率分别为6.1%和26%。通过对实验结果分析表明，光纤基质材料中大量的OH基团对2 μm激光存在严重吸收，是限制激光输出功率和斜率效率的重要因素。为提高激光输出光束质量和输出功率，制备了低OH—含量的锗酸盐单模双包层光纤，在793 nm LD泵浦下，从一根75 cm长的光纤中获得了0.7 W的2 μm激光输出，斜率效率达到21.85%, 光束质量M2因子为1.5。为了提高光纤的强度和抗热损伤性能，研究了不同SiO2含量对掺Tm3+锗硅铅玻璃的物理性质和2 μm光谱性质的影响。随着SiO2含量从0增加至15 mol%，Tm3+离子在2 μm波段的自发辐射系数和受激发射截面分别从315.3 s-1下降至249.1 s-1，6.48×10-21 cm2下降至5.14×10-21 cm2，光谱性质有所下降。但Tg点从472℃上升至496℃，玻璃的硬度从2.96 GPa上升至3.3 GPa，这有利于提高光纤的抗热损伤性和强度。 第五章分析了Ho3+单掺和Tm3+/Ho3+共掺锗铅玻璃的2.1 μm光谱性质。在640 nm LD的泵浦下，研究了Ho3+离子2.1 μm的荧光强度和5I7能级寿命随着浓度增加的变化。Ho3+离子5I7→5I8的自发辐射跃迁几率为94.5 s-1，峰值受激发射截面位于2010 nm处，为4.46×10-21 cm2。明确了Ho3+离子5I7能级寿命淬灭机制主要是Ho3+离子向OH基团传递能量。通过除去OH基团，在Ho3+离子掺杂浓度为6×1020 cm-3时，材料增益指数(τm×NHo)从11.5×1020 ms/cm3提高至30.26×1020 ms/ cm3，而量子效率从17.8%提高至47.1%，增益性能显著提高。探讨了在808 nm LD泵浦下，不同Ho2O3掺杂浓度对Tm3+/Ho3+共掺2.1 μm波段的光谱性质和能量传递过程的影响。固定Tm2O3掺杂浓度为 2 wt%不变，当Ho2O3掺杂浓度为1 wt%时，Ho3+离子5I7→5I8跃迁产生的荧光强度最大，Tm3+离子3F4能级向Ho3+离子5I7能级的能量传递效率为90.3%。当Ho2O3掺杂浓度增加至2 wt%时，传递效率增加至95%。计算得到Tm3+离子3F4能级向Ho3+离子5I7能级的正向微观能量传递系数为34.28×10-40 cm6/s，而反向微观传递系数为1.89×10-40 cm6/s，正向传递系数是反向传递系数的18倍，进一步表明Tm3+离子和Ho3+离子之间的能量传递过程主要是Tm3+离子向Ho3+离子的正向能量传递。因此，用800 nm LD泵浦这种Tm3+/Ho3+共掺锗铅玻璃是一种获得2.1 μm激光输出的有效方式。 最后是论文的结论部分，总结了全文的实验结果，并指出了本论文创新点、不足和展望。 |
| 英文摘要 | Recently, 2~3 μm solid-state lasers have drawn considerable attention due to their wide and important applications, including medical treatment, environmental monitoring, military defense, and so on. As the basement of the development of laser and laser technique, high-performance laser materials is worth to be researched. The motivation of this study is to find suitable host glasses for 2~3 μm fiber lasers. The physical properties, spectroscopic characterizations and laser performance of germanate and tellurite glasses and fibers have been investigated and analyzed. This dissertation includes the following six chapters. The first chapter is the literature review, and chapter two is the experimental methods and theoretical basis. chapter three, four and five are the core contents of the dissertation. The last chapter is the conclusion. In chapter one, fundamental theory, construction and applications of laser and fiber laser are briefly introduced firstly. Then, the realization and application of 2~3 μm laser have been presented. Later, the research progresses and current status on rare earth doped mid-IR glass fibers and lasers have been reviewed briefly. At last, the purpose and research topics of the dissertation were put forward. In chapter two, the experimental methods and testing tools are introduced, including preparation of glass samples, fabrication of fibers, measurements of physical and spectroscopic properties. The theories for analyzing the experimental data are reviewed as well. In chapter three, spectroscopic properties of 2.7 μm emission in Er3+ and Er3+/Pr3+ codoped tellurite glasses have been studied. Firstly, the variation of emission intensity at 2.7 μm with different doping concentration of Er3+ ions has been analyzed under the excitation of 980 nm LD. The intensity of 2.7 μm is enhanced with the increasing of Er2O3 from 0.1 mol% to 3 mol%. No crystallization peak is observed from DSC curve of the glass sample doped with 3 mol% Er2O3, indicating a good thermalstability of the glass. The spontaneous radiative rate and branching ratio of 2.7 μm are 57.8 s 1 and 17.3%, respectively. The maximum emission cross section is 1.12×10-20 cm2 at 2708 nm. Fluorescence properties and energy transfer mechanism in Er3+/Pr3+ codoped tellurite glass have been investigated. According to experimental results, few Pr3+ ions could depopulate the 4I13/2 level obviously while have barely influence on the population of 4I11/2 level. Therefore, Er3+/Pr3+-codoping in this tellurite glass is an efficient way to built population inversion between 4I11/2 and 4I13/2 level. But the ratio of Pr3+ to Er3+ ions concentration and concentration of Pr3+ ions must be optimized to balance the gain properties and pump threshold. In chapter four, the Tm3+-doped germanate glasses and fibers have been designed and prepared, and the 2 μm spectral properties and laser performance have been measured and analyzed. Firstly, the 2 μm emission properties and lifetime of 3F4 level in Tm3+ doped lead-germanate glass with different Tm2O3 concentration are presented. The maximum 2 μm emission intensity is achieved in the sample doped with 2 wt% Tm2O3, the measured lifetime of 3F4 level is 1.5 ms, and the corresponding quantum efficiency is 45.5%. The maximum emission cross section is 6.15×10-21 cm2 at 1864 nm. This lead-germanate glass shows excellent 2 μm emission properties. Then, single cladding fiber with a 2 wt% Tm2O3 doped core has been fabricated. The measured propagation loss is 3.12 dB/m at 1310 nm. Laser output has been demonstrated from the multi-mode fibers, pumping by 793 nm LD and 1590 nm fiber laser, respectively. The maximum output power are 95 mW and 44.7 mW. Correspondingly, the slope efficiency is 6.1% and 26% , respectively. Severe absorption at 2 μm induced by large amount of OH groups in the glass is responsible for limiting the laser output power and slope efficiency. In order to improve the laser performance, the single-mode double-cladding fiber with low OH groups content has been prepared later. The maximum output power of 0.7 W, with a slope efficiency of 21.85%, has been achieved from a 75 cm long fiber, the measured beam quality is ~1.5. With the purpose of enhancing the strength and thermal damage resistance threshold of germanate fiber, SiO2 was introduced into the original composition. Physical and spectral properties of Tm3+ doped germanate glasses with different SiO2 content have been studied. With increase of SiO2 content from 0 to 15 mol%, the spontaneous radiative coefficient and stimulated emission cross section of 3F4→3H6 transition are decreased from 315.3 s-1 to 249.1 s-1, 6.48×10-21 cm2 to 5.14×10-21 cm2, respectively, which means a degradation of spectral properties. However, the transition temperature of glasses increased from 472 ℃ to 496 ℃, and the hardness increased from 2.96 GPa to 3.3 GPa. Therefore, the addition of SiO2 could improve the strength and thermal damage resistance threshold of germanate fiber while the spectral properties are sacrificed moderately. In chapter five, 2.1 μm spectral properties of Ho3+ and Tm3+/Ho3+ codoped lead-germanate glasses have been studied. The effect of Ho3+ ions concentration on the 2.1 μm emission intensity and the lifetime of 5I7 level has been investigated pumped by a 640 nm LD. The spontaneous radiative rate of 5I7→5I8 transition is 94.5 s-1, the maximum stimulated emission cross section is 4.46×10-21 cm2 at 2010 nm. The energy transfer process to OH groups dominates the lifetime quenching process of 5I7 of Ho3+ ions. By eliminating the OH groups, the index of materials gain (τm×NHo) is increased from 11.5×1020 ms/cm3 to 30.26×1020 ms/cm3, and the corresponding quantum efficiency is improved from 17.8% to 47.1%, when the doping concentration of Ho3+ ions is fixed to 6×1020 cm-3. With the excitation of 808 nm LD, the influence of Ho2O3 concentration on 2.1 μm spectral properties and energy transfer process in Tm3+/Ho3+ codoped lead-germanate glasses have been investigated. The glass doped with 2 wt% Tm2O3 and 1 wt% Ho2O3 has the strongest 2.1 μm emission intensity, and the corresponding energy transfer efficiency from Tm3+ to Ho3+ is 90.3%. When the Ho2O3 doping concentration is increased to 2 wt%, the energy transfer efficiency is improved to 95%. The microscopic energy transfer parameters of Tm3+ to Ho3+ and Ho3+ to Tm3+ ions are calculated to be 34.28×10-40 cm6/s and 1.89×10-40 cm6/s, respectively. The results show that the energy transfer from Tm3+ to Ho3+ is more effective. Therefore, pumping this Tm3+/Ho3+ codoped lead-germanate glass by 800 nm LD is an efficient way to get 2.1 μm laser output. The last chapter is the conclusion. All results of present works have been concluded in this chapter. The innovation, shortage and outlook of this dissertation have been pointed out as well. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15937]  |
| 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 | 范小康. 掺稀土碲酸盐、锗酸盐玻璃与光纤2~3μm光谱和激光性能[D]. 中国科学院上海光学精密机械研究所. 2015. |
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