【作者】 张强；

【导师】 袁树忠；

【作者基本信息】 南开大学 ， 光学， 2004， 硕士

【摘要】 掺稀土光纤激光器结构紧凑，具有良好的散热特性和很高的转换效率，使其在光纤通信、传感、测量及工业加工等方面被广泛的应用，成为近年来倍受关注的有源光纤器件。而掺镱双包层光纤激光器又以其宽的光谱特性、高的转换效率和输出功率，受到人们普遍的关注。 本文介绍了掺镱双包层光纤激光器的研究进展和应用前景，从实验和理论两方面研究了结构参数对掺镱双包层光纤激光器的输出特性的影响；对双包层光纤Bragg光栅的工作原理、写制过程及光谱特性进行了论述；介绍了双包层激光器各种泵浦方式的研究现状，提出并详细分析了三种新型的耦合方式；在双包层光栅选频和调谐、多波长以及高功率等方面实验研究了掺镱双包层光纤激光器。主要内容如下： 1．双包层光纤激光器的理论分析 从镱离子稳态时的速率方程和泵浦光、激光在双包层光纤中的前后向传输方程出发，采用一种简化的理论模型，推导了光纤激光器输出特性与激光腔参数关系的解析表达式。 数值模拟分析了泵浦光功率沿双包层光纤的分布情况和激光输出功率与泵浦光功率的关系；进一步研究了泵浦光和激光波长、增益光纤长度和前、后腔镜反射率R₁、R₂等结构参数对掺镱双包层光纤激光器最大输出功率、泵浦阈值、斜率效率及输出波长等输出特性的影响，为具体的实验研究提供了理论依据。 根据光纤Bragg光栅作腔镜的光纤激光器的特点，通过修改最初建立的简化模型，给出了相应的解析解。 2．光纤光栅的理论研究及制作 采用耦合模理论，分析了各个模式的激光在光纤光栅内传播时功率转换趋势以及选频机制，推导了光纤Bragg光栅的反射率、Bragg波长和3dB带宽等参数的表达式；在对单包层光纤Bragg光栅进行理论分析的基础上，就有限包层半径的具体情况，进行了理论分析，并对通信中常用SMF-28^TM类型光纤进行了数值模拟，得出结论：只有外包层直径在小于16.3μm时，外包层折射率变化才会对基模有效折射率的改变产生显著的影响。 介绍了全息法和相位掩模法等写制光栅的方法，并利用相位掩模法在掺镱双包层光纤载氢前后，在不同内包层形状的光纤上进行写制实验，得到了不同更多还原

【Abstract】 Because rare-earth doped fiber lasers have many applications in optical communication, sensing, measuring and industrial fabrication for their compact structures, wonderful heat-sinking capability and highly conversion efficiency, they are studied more and more as source fiber devices. With the wide spectra, high conversion efficiency and high output power, double-clad Yb³⁺-doped fiber lasers （YDFL） will play more and more important role in future.There are the research progress and prosperous future of the double-clad YDFL in this thesis. Not only in theory but also in practice, the influence to output characteristic by the parameters of double-clad YDFL is studied. It is also introduced that the working principle, fabrication process and spectra characteristics of the double-clad fiber Bragg gratings （FBG）. We show the latest status of cladding pump technology, and analyze three kinds of coupling methods in detail. We also study the double-clad YDFL in the ways of multiple wavelengthes, selecting frequency by double-clad FBQ and high power in practice. Main works are abstracted as follows:1. Theoretical research on double-clad fiber lasersThrough a new model, we got the explicit expressions of the output characteristics and the cavity parameters of the double-clad fiber lasers. The distribution of the power of pump laser and the relation between the output power and the pump power were analyzed by the method of numerical simulation. We further studied the influence to the maximum output power, threshold power, slope efficiency and output wavelength by the wavelength of pump and signal laser, fiber length and reflectance of both the front and back cavity mirrors of the double-clad YDFL. Then we got the theoretical foundation of the later experiments.By revising the original simplified model, we got the explicit results on the basis of the traits of FBG.2. The fabrication and theoretical research of FBGBy using coupled-mode theory, we analyzed the conversion between different modes in the FBG and the scheme of selecting frequency, worked out the expression of the parameters of FBQ numerically simulated the FBG in practice and discussed the results. With the phase-mask method, we made FBG in double-clad Yb³⁺-doped fibers with different inner sections, reflectance, and output wavelength, then analyzed the results theoretically.更多还原