| 题名 | 稀土掺杂硅酸盐玻璃和光纤~2μm荧光、激光特性的研究 |
| 作者 | 刘雪强 |
| 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 | 陈丹平 |
| 关键词 | 硅酸盐玻璃 ~2μm荧光 光纤激光 Tm3+ Ho3+ |
| 其他题名 | ~2 μm luminescence and laser properties of rare earth ion doped silicate glasses and fibers |
| 中文摘要 | ~2 μm光纤激光在军事、医疗和遥感探测等方面有着广阔的应用前景和重要的应用价值。~2 μm激光波长范围为1.87-2.16 μm，处于大气窗口，涵盖了水分子和 CO2 分子的吸收带，同时又是人眼安全的。~2 μm激光器也是3-5 μm光学参量振荡器以及超连续谱的理想泵浦源。基于以上特点，~2 μm激光材料的研究具有重要的意义。 稀土离子掺杂石英光纤由于化学稳定性好、损耗低、机械强度高而用于高功率光纤激光器。但是其稀土离子掺杂浓度较低，对于单频光纤激光器，往往要求光纤长度非常短，因此光纤要具有较高的稀土离子掺杂浓度。与石英玻璃相比，硅酸玻璃中的网络外体破坏了网络结构，提供了更多空隙位置，因此可以容纳更多稀土离子。与氟化物玻璃，重金属氧化物玻璃等其它多组分玻璃相比，硅酸盐玻璃具有较高的机械强度，这有利于其实现与石英光纤的熔接。同时，硅酸盐玻璃具有较高的稳定性，易于制备光纤。硅酸盐玻璃的原料也比较便宜，有利于其商用化。国外虽然有~2 μm硅酸盐光纤激光的报道，但是国内目前还未见报道。 一种适合~2 μm光纤激光的玻璃材料有三个基本要求：高的玻璃稳定性、高的机械强度和高的增益能力。高的玻璃稳定性是指玻璃在拉制光纤过程中不会出现析晶、分相等现象。高的机械强度有利于其实现与石英光纤的熔接。高的增益能力要求玻璃具有较高的稀土离子溶解度，较低的羟基含量，较高的发射截面（或者较高的自发辐射跃迁几率）和适中的声子能量等。本论文是从硅酸盐玻璃基质出发寻找一款玻璃稳定性好、机械强度高和增益能力高的~2 μm光纤用玻璃基质，然后制备光纤并表征其光纤激光性能。本论文总共包括八章，前两章分别为文献综述和实验方法及稀土发光理论，第三、四、五、六、七章是详细的研究内容，包括从Tm3+ 发光机理到基质玻璃的选择再到光纤的制备和表征，第八章是结论。 第一章文献综述主要介绍了~2 μm光纤激光的应用，~2 μm光纤激光机理，光纤预制棒制备方法，~2 μm光纤激光玻璃基质及研究进展以及本论文的研究目的和内容。 第二章是实验方法和理论计算，主要介绍了玻璃样品和光纤制备，玻璃样品性能的测试方法，J-O 理论，吸收和发射截面计算方法，能量传递以及多声子弛豫。 第三章主要是讨论了Tm3+ 在硅酸盐玻璃基质中的发光机理。以SACB玻璃为基质，对比引入氟化物之后玻璃性能的变化。根据声子边带谱计算了在SACB和SACBF玻璃中Tm3+ 各能级之间的多声子弛豫速率。从吸收光谱和荧光光谱出发计算了能量转移EM和交叉弛豫CR速率。根据跳跃模型计算了Tm3+ 之间的能量传递速率ET。结合速率方程和荧光光谱，计算了SACB和SACBF中的羟基猝灭速率。发现引入氟化物之后，羟基猝灭速率从550 s-1降低到283 s-1。同时对除水条件进行了探索，发现熔制小块玻璃时，要保证通氧气时间长于60 min才能较好得除去玻璃中的羟基。 第四章比较了Tm3+ 掺杂不同硅酸盐玻璃基质的性能。比较了SACB、 SANB以及SPANK三种组分的机械性能和发光性能。与其它两种组分相比，SPANK组分具有较大的峰值发射截面，较高的量子效率，较长的荧光寿命，较大的增益系数G以及较大的品质因子FOM。因此SPANK组分很适合用作光纤激光的玻璃基质。 第五章主要是探索了Tm3+ 掺杂铅硅酸盐玻璃光纤的制备。选定SPANK为光纤玻璃基质，通过最优化浓度实验发现SPANK基质玻璃中的最佳掺杂浓度为3wt%。采用堆垛法制备了双包层光纤，纤芯所用玻璃为掺杂浓度3wt%的SPANK玻璃。当泵浦功率达到17 W时，~2 μm激光功率达到了70 mW。当泵浦功率进一步增大时，由于积累了大量的热量，光纤弯曲。这里产生的大量热量主要来源于光纤较高的损耗和羟基引起的无辐射弛豫。采用高纯度原料熔制玻璃，改善玻璃的熔制条件，使玻璃中的羟基吸收系数从1.7 cm-1降低到0.2 cm-1。采用堆垛法制备了单包层光纤，光纤的损耗降低到5dB/m。在793 nm半导体激光器泵浦下，最高实现了1.57 W激光输出，激光斜率效率为27.5%。同时制备了长度约为2 cm的光纤陶瓷插芯，在1590 nm同带泵浦下，最高实现了25 mW的激光输出，激光斜率效率为30%。这表明该光纤有潜力应用到~2 μm单频光纤激光器。 第六章研究了Ho3+ 掺杂玻璃发光性能以及Ho3+ 掺杂铅硅酸盐玻璃光纤的制备。发现随着氧化铅含量增加，Ho3+: 5I7能级荧光寿命逐渐增加。这是由理论寿命τrad增加和多声子弛豫速率降低引起的。虽然自发辐射跃迁几率A10随PbO含量增加而降低，但是多声子弛豫速率W10降低得比A10更快。最终，荧光强度随着PbO含量增加而增加。制备了Ho3+ 掺杂浓度高达5.91×1020 cm-3的块体玻璃，Ho3+: 5I7荧光寿命长达1.41 ms。制备了Ho3+: SPANK单包层光纤，纤芯在1940 nm处的吸收为2.34 dB/cm。用Tm3+ 掺杂石英光纤激光同带泵浦一段6 cm长的Ho3+: SPANK单包层光纤，最高实现了60 mW的单模激光输出。 第七章主要研究了Er3+/Tm3+ 与Er3+/Ho3+ 共掺铅硅酸盐玻璃的发光性能。对于单频光纤激光器，高的光纤吸收系数是基本要求。通过引入Er3+ 可以显著提高其在1550 nm处的吸收系数，研究了Er3+/Tm3+、Er3+/Ho3+ 的能量传递机理。在E0.5T1.5样品中，Er3+?: 4I13/2与? Tm3+: 3F4能级之间的能量传递效率达到96.6%。而在E0.5H1.5样品中，Er3+?: 4I13/2与Ho3+: 5I7 能级的能量传递效率也达到86.0%。可以发现，Er3+ 对Tm3+ 与Ho3+ 都可以起到很好的敏化作用。 最后是论文的结论部分，总结了全文的实验结果，指出了本论文的创新点和不足之处。 |
| 英文摘要 | ~2 μm fiber lasers are highly potential for applications in military, medical surgery, and remote sensing. Generally, ~2 μm wavelength covers from 1.87-2.16 μm. Both water and carbon oxide have absorption band in this range. Furthermore, it is eye-safe and has good transmission in the air. ~2 μm lasers could also act as pump sources for longer wavelength generation, supercontinuum generation and OPO. Thus, it is of great significance to study laser materials for ~2 μm lasers. As is known, rare earth ion doped silica fibers have been widely used in high power scaling owing to its low loss, high stability, and high mechanical intensity. However, solubility of silica fiber is relatively low. For applications such as single frequency fiber lasers, usually centimeters long fiber is needed. Here the fiber must have a high solublity of rare earth ions. Compared to silica glass, silicate glass is not only composed of silica, but also contains network modifiers such as alkali, alkaline earth ions and so on. These modifiers break the network and provide more space for rare earth ions. Thus, silicate glass has a much higher solubility of rare earth ions than silica. Compared to fluoride glass and heavy metal oxide glass, silicate glass has a much higher strength. Thus, it is easier for silicate glass fiber to splice with commercial silica fiber. Moreover, high glass stability and cheap raw materials of silicate fiber contribute to its commercialization. There are some reports on ~2 μm lasers from a silicate fiber abroad. However, progress on rare earth ion doped silicate glass fibers in China is really slow. High glass stability, high mehechnical intesntity, and high gain ability are necessary for a ~2 μm fiber material. During the fiber drawing, no crystallization or phase separation should appear. High mehechnical intensity ensures glass fiber could splice with commercial silica fiber. To achieve a high gain ability in a glass, high solublity of rare earth ions, low content of hydroxyls, high emission cross section or high spontaneous transiton rate, and moderate phonon energy of a glass material are necessary. In this dissertation, we aim to find a silicate glass with high mehechnical intensity, high glass stability, and high gain ability and explore corresponding fibers for ~2 μm fiber lasers. It mainly includes eight chapters. The first two chapters are literature review, experimental methods, and theories on luminescence of rare earth ions. Chapters 3-7 are core part of this dissertation, including luminescence mechanism of Tm3+, properties of glasses, and fiber lasers. Chapter 8 is the conclusion. Chapter I mainly introduces applications of ~2 μm fiber lasers, fundamentals of ~2 μm fiber lasers, preparation methods of fiber preforms, progress of ~2 μm fiber lasers, and purpose and contents of this dissertation. Chapter II is experimental methods and theoretical calculation. It mainly includes preparation of glasses and fibers, characterization methods of glass properties, Judd-Oflet theory, methods of calculating absorption and emission cross sections, energy migration, and multi-phonon relaxation. Chapter III talks about luminescence mechanism of Tm3+ in silicate glass. SACB glass is chosen as the matrix. Mechanical property and luminescent property of glass are compared before and after addition of fluoride. Multi-phonon relaxation rates are calculated based on phonon side band spectrum. Energy migration rate EM, cross relaxation rate CR, and energy transfer rate ET are also calculated. Combining numerical formula and luminescence spectra, quenching rate of hydroxyls is calculated. As a result, it decreases from 550 s-1 to 283 s-1 after addition of fluoride. Moreover, hydroxyls removment condition is optimized. For small batches of glass, bubbling oxygen time should be at least 60 min. Chapter IV compares luminescent properties of Tm3+ in different glass matrixes. Mechanical and luminescent properties of SACB, SANB, and SPANK compositions are analyzed. Compared to the other two compositions, SPANK has the higher emission cross section, higher quantum efficiency, longer lifetime, higher gain coefficient, and larger FOM. Thus, SPANK is a highly promising matrix for ~2 μm fiber lasers. Chapter V explores preparation of Tm3+ -doped lead silicate glass fiber. Based on above exploration, SPANK is chosen as the matrix for fibers. Optimized doping concentration is ascertained to be 3wt%. A double cladding fiber preform is prepared with stack-and-draw method. When pump power reaches 17 W, 70 mW ~2 μm laser output is realized. When pump power further increases, the fiber bends owing to large amount of heat accumulated. These heat are on one part ascribed to large loss of the fiber. The other may be high non-radiative relaxation rate such as quenching of hydroxyls. We optimize the fibers by improving purity of raw materials and glass melting conditions. Absorption of hydroxyls decreases from 1.7 cm-1 to 0.2 cm-1. Loss of the fiber decreases to 5dB/m. A single cladding fiber is prepared. Under pump of 793 LD, a maximum power of 1.57 W is realized. The corresponding slope efficiency is fitted to be 27.5%. Moreover, a 2 cm-long fiber is also prepared. Under pump of a 1590 nm laser, a maximum 25 mW is realized. The slope efficiency is fitted to be 30%. These results indicate Tm3+-doped lead silicate glass fiber is highly potential for ~2 μm fiber lasers. Chapter VI investigates properties of Ho3+-doped glasses and Ho3+-doped lead silicate glass fiber. It is found that lifetime of 5I7 increases with increment of PbO in lead silicate glass. One factor is theoretical lifetime τrad increases. The other is multi-phonon relaxation rate decreases. Though spontaneous transition rate A10 decreases with increment of PbO, multi-phonon relaxation rate decreases more rapidly. As a result, luminescent intensity of Ho3+-doped glasses increases with increasing PbO content. Moreover, a large batch of lead silicate glass with Ho3+ doping concentration 5.91×1020 cm-3 is prepared. Lifetime of Ho3+: 5I7 is as long as 1.41 ms. A single cladding fiber is prepared, which has an absorption of 2.34 dB/cm. Pumped by a Tm3+-doped silica fiber laser, a maximum of 60 mW at 2040 nm is generated from a 6 cm-long fiber. Chapter VII investigates luminescent properties of Er3+/Tm3+ co-doped and Er3+/Ho3+ co-doped lead silicate glass. For single frequency fiber lasers, high absorption is necessary. Here Er3+ is introduced as a sensitizer for Tm3+ and Ho3+ and energy transfer mechanism is investigated. In E0.5T1.5 sample, the energy transfer rate from Er3+?: 4I13 to? Tm3+: 3F4 could reach 96.6%. In E0.5H1.5 sample, the energy transfer rate from Er3+?: 4I13 to? Ho3+: 5I7 could reach 86.0%. Thus, Er3+? could act as a good sensitizer for Tm3+ and Ho3+. The last chapter is the conclusion. All results of present work are concluded in this chapter. The innovation and shortage of this dissertation are also mentioned. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15994]  |
| 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 | 刘雪强. 稀土掺杂硅酸盐玻璃和光纤~2μm荧光、激光特性的研究[D]. 中国科学院上海光学精密机械研究所. 2016. |
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