【作者】 朱志武；

【导师】 冯莹；

【作者基本信息】 国防科学技术大学 ， 光学工程， 2005， 硕士

【摘要】 由于双包层光纤的特殊结构和稀土镱离子的优异性能,近年来双包层光纤激光器发展迅速,越来越受到人们的重视。本文首先论述了双包层光纤激光器的发展现状以及泵浦耦合技术,接下来从泵浦方式的角度深入研究了采用空间多点泵浦方式的光纤激光器的输出特性,为下一步将要展开的实验研究工作进行理论及技术方案上的准备。研究工作主要包括:1、分析了镱离子工作的四能级系统,在近似求解稳态速率方程组的基础上得出了光纤激光器输出功率的解析表达式,并且计算了解析解与数值解的偏差。2、针对稳态速率方程组的特点,提出了新的数值求解方法。研究端面泵浦方式和多点泵浦方式的特点,分别建立了数学模型。两种新方法均有较简单的思路,很好的解决了微分方程组的数值求解问题。其中端面泵浦算法有较高的计算速度,多点泵浦算法有很高的可靠性。3、利用前面建立的数学模型进行双包层光纤激光器的数值分析,重点研究了多点泵浦的功率扩展作用以及多点泵浦情况下光纤的最佳长度和各泵浦点的功率分配原则,特别是首次研究了在泵浦光反射限制条件下,光纤长度的优化问题。4、首次研究了采用多点泵浦的技术方案时,各泵浦点处的损耗对光纤激光器输出功率的影响程度,分析了有损耗存在情况下的多点泵浦方式的局限性。5、对高功率光纤激光器的热效应进行了研究,利用理论分析和数值求解相结合的方法,研究了两种改善热效应的方法,其中重点分析了多点泵浦对高功率光纤激光器热效应的改善,结果证明多点泵浦的技术方案是抑制热效应的有效途径。6、将双包层光纤激光器的输出特性分析结果和热效应的分析结果做了对比分析,提出了高功率双包层光纤激光器设计的一般步骤,即首先考虑热效应然后再进行光纤长度的优化设计。通过对多点泵浦光纤激光器的数值和理论分析,得出了一些有用的结论,这些结论对双包层光纤激光器的结构优化具有指导意义。更多还原

【Abstract】 Benefit from the particular structure of the double-clad fibers (DCF) and the excellent performance of Yb3+, double-clad fiber lasers (DCFLs) are being developed rapidly these years. Firstly, the pump light coupling technology is introduced in this paper, and the developing situation is summarized, furthermore, the output performance of multi-point pump DCFLs is researched deeply. The research work primarily concludes as follows:1. The steady rate equations are get under the analysis of four energy class of Yb3+, and the approximate resolution is carried out.2. The new numerical resolution is get under the analysis of the physics problem. Among them, the end-pump arithmetic has fast resolution velocity, and the multi-point pump arithmetic has high reliability.3. Some problems of multi-point pump are researched deeply, and depend on this some useful conclusions are get to optimize the design of DCFLs.4. The loss of the pump points is took into account for the fist time in this paper, the limitation of multi-point pump is put forward.5. The thermal effect is studied as well in this dissertation, particularly, the temperature distribution along fiber under multi-point pump is brought forward, and the improvement of thermal effect under multi-point pump is researched as well.6. Upon the analysis of the output performance and the thermal effect of DCFLs, the processes of the DCFLs design are brought forward.To sum it up, some optimization methods of the DCFLs design are gained in this dissertation, and all these methods can conduct the experiment of DCFLs.更多还原