短腔磷酸盐玻璃光纤激光器及其输出特性研究
文献类型：学位论文
| 作者 | 孟莉 |
| 学位类别 | 硕士 |
| 答辩日期 | 2009 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 蔡海文 |
| 关键词 | 光纤激光器 窄线宽 磷酸盐玻璃光纤 |
| 其他题名 | A Short-Cavity Phosphate Glass Fiber Laser and Its Output Characteristics |
| 中文摘要 | 单纵模光纤激光器具有线宽窄、光束质量好、转换效率高和全光纤集成稳定性好等突出优点，在光纤通讯、光纤传感和相干激光雷达等重要领域有着广泛的应用。为了加大纵模间隔，获得稳定的单纵模运转，采用短腔是一个有效途径。常规稀土掺杂石英光纤由于稀土离子溶解度低，短腔难以获得足够的增益。磷酸盐玻璃光纤具有高的稀土离子可溶性，掺杂浓度比石英光纤高，增益系数比石英光纤大两个数量级，因此可以应用在直线短腔结构中解决缩短腔长与提高功率的矛盾，实现高功率单纵模输出。基于高掺杂磷酸盐玻璃的光纤激光器已经成为光纤激光器领域的新热点。本文在对国产铒镱共掺磷酸盐玻璃光纤基本特性测试研究的基础上，研制了直线短腔结构铒镱共掺磷酸盐玻璃光纤激光器，获得了较大功率的单频窄线宽激光输出，并重点研究了激光输出随温度变化的特性。本文的主要内容包括以下内容： 本文对光纤激光器的输出特性进行了理论分析和数值模拟计算，从简化二能级速率方程出发推导出了泵浦阈值、输出功率和斜率效率的解析表达式。通过对模拟结果的分析，发现对于一定的有源光纤长度存在一个最优耦合输出腔镜的反射率以获得最大的输出斜率效率，这对光纤激光器的设计具有一定的指导意义。本文还讨论了激光器线宽理论和直线腔激光器单模运转理论。直线腔激光器的纵模增益和损耗满足特定条件，就可以克服空间烧孔效应而实现单纵模振荡。 本文对国产铒镱共掺磷酸盐玻璃光纤的吸收和增益特性进行了测试分析，发现其具备很高的吸收和增益系数。最佳泵浦光波长为975nm，在1535nm处有最高的净增益，最大增益系数为4.2dB/cm；泵浦功率为零时，有最大吸收系数，吸收系数为8.0 dB/cm。采用低精细度法布里珀罗干涉方法，测量得到了磷酸盐玻璃光纤的折射率和热光系数为1.5195和 ℃-1。从理论和实验方面都对应用为光纤激光器的谐振腔腔镜的光纤光栅的特性做了研究。采用1cm长度的这种光纤，利用光纤光栅作为输出腔镜，本文研制了直线短腔结构单纵模光纤激光器，边模抑制比大于50dB，线宽为4.5kHz。同时，还分别测试了激光器的输出波长和输出功率随热沉温度的变化曲线。当激光器热沉温度稳定在11℃，激光输出斜率效率达24%，泵浦功率为415mW时，输出功率达79mW。实验测试发现，激光输出功率不是随温度单调变化，而是呈现波动的特性，波动周期与泵浦功率有关，在13℃-20℃范围内变化；在高泵浦功率下输出功率有饱和的趋势，饱和点的位置随温度也有所变化，并且对这一现象进行了讨论和分析。为提高输出功率、能量转换效率和稳定性，有必要在保证材料光学性质的条件下继续提高Er/Yb的掺杂浓度，并对激光器进行温控。 |
| 英文摘要 | Due to the merits of narrow line width, good beam quality, high efficiency, all-fiber construction and good integration, the single-frequency fiber laser is the ideal source for optical communication, optical sensing and LIDAR systems. It’s an effective way to obtain single longitudinal mode (SLM) operation by shortening the length of the resonant cavity thus widening the free spectral range. However, low concentration of rare earth ion in ordinary silica fiber made it hard for short linear fiber laser to obtain enough gain to output large power. Phosphate glass fiber has a high solubility for rear earth ions, so it can be more heavily doped then silica fiber can be. Then, phosphate glass fiber can offer higher gain, nearly a hundred times higher than silica fiber can. So heavily doped phosphate glass fiber is a kind of perfect gain material for short cavity linear fiber laser to output a single-frequency and large power output, which compromise shortening the cavity and increasing the output power. The fiber laser based on the phosphate glass fiber has became the focus of the fiber laser. In this dissertation, on the basic of research of the phosphate glass fiber made in china, we designed and realized a short-cavity linear Er-Yb codoped phosphate glass fiber laser to obtain a single-frequency, narrow linewidthe and large power output, and we focus on the relation of output of the fiber laser to temperature. This dissertation includes followings: In this dissertation, the output of the fiber laser is researched theoretically and numerically-analog-calculated. Using simplified two-level rate equations, the analytical solution of output characteristics is developed, including pump threshold, output power and slope efficiency. From the results of numerical simulation, it’s found that reflectivity of the output coupled fiber grating should be optimized for a fix length of the gain fiber to get a higher output efficiency, which is important for the design of the fiber laser. The theory of line width of laser and linear cavity SLM fiber laser is also deduced. It is illustrated that spatial hole burning in linear cavity can be overcome if some special requirements are satisfied. Measurements of the gain of the Er-Yb co-doped phosphate glass fiber shows that when it’s pumped by 975 nm, the 1535 nm laser has the highest gain of 4.2dB/cm, and maximum absorption of 8.0 dB/cm without pump power. By taking the glass fiber as medium of a low finesse F-P cavity, refractive index and optic-thermal coefficient of the phosphate glass fiber is measured to be 1.5195 in 1530-1550nm band and oC-1. The properties of the fiber grating are also researched theoretically and experimentally. Though utilizing Er-Yb co-doped phosphate fiber glass fiber and fiber grating, the SLM fiber linear laser is realized to be able to output a single-frequency, narrow line width and high slope efficiency. The fiber laser output spectrum shows single longitudinal mode operation at 1534nm with side mode suppressing ratio (SMSR) above 50 dB. Homodyne measurement gives its line width as narrow as 4.5 kHz.. Relation of the output wavelength of the fiber laser and output power to heat sink temperature is measured respectively. When the heat sink temperature is stabilized at 11℃, the slope efficiency is 24%; and its output power reaches 79mW under pump power of 415 mW. It is found that the output power changes with the sink temperature periodically and the period fluctuates in the range of 13℃-20℃ with different pump power. It’s also found slope efficiency decreases at higher pump power range and the output power increases sub-linearly. This phenomenon is discussed qualitatively. To increase the output power and slope efficiency, it’s necessary to increase the solution of the Er/Yb in the phosphate glass fiber under the guarantee of the optical property of the phosphate glass fiber and stabilized the sink temperature. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16412]  |
| 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 | 孟莉. 短腔磷酸盐玻璃光纤激光器及其输出特性研究[D]. 中国科学院上海光学精密机械研究所. 2009. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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