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题名	全光纤化高功率光纤激光器理论及实验研究
作者	范元媛
学位类别	博士
答辩日期	2012
授予单位	中国科学院上海光学精密机械研究所
导师	周军
关键词	高功率光纤激光器 全光纤化结构 光纤光栅 热效应 热管理
其他题名	Theoretical and experimental study on all-fiber high power fiber lasers
中文摘要	高功率光纤激光器是目前激光技术领域最为活跃的研究方向之一。由于其具有结构紧凑、稳定性好、转换效率高、光束质量好等一系列优点，在激光先进制造、激光医疗、国防军事等领域有着重要应用。特种有源光纤、尾纤化泵浦源及光纤化无源器件直接熔接的全光纤化结构方案，由于摆脱了传统的空间光学元件，减小了光学界面，使得高功率激光的产生和传输均可在柔性化的光纤中进行，提高了光纤激光器的可靠性和稳定性。本论文主要对全光纤化高功率光纤激光器技术进行了详细的理论和实验研究。 第一章综述了高功率光纤激光器的基本原理、分类、特点、典型应用和发展前景，并从尾纤化泵浦源及泵浦耦合技术、双包层有源光纤、光纤化无源器件、光纤输出准直技术等四个方面简要介绍了全光纤化高功率光纤激光器所涉及到的关键技术、核心材料与部件。 第二章对构成高功率全光纤激光器不可或缺的关键器件——双包层光纤光栅（FBG）及其激光特性进行了研究。对FBG设计与制作中涉及到的问题进行了探讨，基于相位掩模法在大模场面积双包层光纤（LMA-DCF）中刻写了FBG，并进行了高功率封装。基于所制备的单个高反FBG和FBGs对，进行了高功率光纤激光实验验证。基于FBGs对的光纤激光器最高输出功率达314 W，激光性能稳定。 第三章基于稳态热传导方程，对高功率光纤激光器中的热效应进行了研究。建立了双包层光纤稳态温度分布模型，模拟了增益光纤中的温度分布，研究了对流换热系数、光纤尺寸、泵浦功率及结构等因素对光纤温度分布的影响，为千瓦级光纤激光系统中增益光纤的散热管理提供了指导。详细分析了光纤熔点热管理的必要性，并引入了用于判定单点散热特性的接触热阻的概念。 第四章对全光纤化高功率光纤激光振荡器进行了理论及实验研究。基于稳态速率方程建立了掺Yb3+双包层光纤激光器（YDCFL）模型，分析了腔镜反射率、增益光纤长度、泵浦结构、泵浦波长、泵浦功率等对激光输出功率的影响，为优化激光腔性能提供指导。对不同泵浦结构、不同泵浦波长的全光纤YDCFL进行了实验研究。在此基础上，设计并实现了高效率的全光纤激光振荡器，利用波长锁定的976 nm泵浦源后向泵浦YDCFL，实现了激光功率550 W、斜率效率达76.4%的激光输出。 第五章对全光纤化高功率光纤放大器进行了理论及实验研究。利用建立的光纤放大器理论模型对不同泵浦功率下的增益光纤长度进行了优化。对无源光纤与增益光纤熔点的冷却进行了理论与实验研究，通过引入金属胶带固定光纤和热界面材料（TIM）填充界面空隙，可实现废热的有效传导，获得良好的冷却效果。基于主振荡功率放大（MOPA）结构，进行了千瓦级光纤激光的实验研究，在种子光功率160 W，泵浦光功率1.22 kW时，实现了1.17 kW的放大激光功率输出，并研制出千瓦级全光纤激光器样机。
英文摘要	High-power fiber laser is one of the most attractive research directions in the laser field. Due to compactness, good stability, high efficiency, and outstanding beam quality, fiber lasers are very important for the present and potential applications including laser advanced manufacturing, laser medicine, defense and military, etc. The all-fiber structure, which is composed of special active fiber, fiber-pigtailed pump sources and fiber passive devices, has improved the reliability and stability of the fiber laser. This is because it has got rid of the traditional bulk space devices and reduced the optical interface, so high-power laser can both generate and transmit in the flexible fiber. In this paper, all-fiber high-power fiber laser technology is researched theoretically and experimentally in detail. In the first chapter, the principle, classification, characteristic, typical applications and developing prospects of high-power fiber lasers are reviewed. The related key techniques, core materials and components involved in all-fiber lasers, as the fiber-pigtailed pump sources, pump coupling techniques, double-clad active fibers, fiber passive devices and output collimating techniques, are briefly introduced. In the second chapter, the double-clad fiber Bragg grating (FBG) which is an indispensable key component for all-fiber laser and its laser characteristics are investigated. The involved design and preparation issues of FBG are discussed. FBGs are inscribed on large-mode-area double-clad fibers (LMA- DCFs) with phase mask techniques, and they are mentally packaged which can sustain high laser power. High-power fiber laser experiments are verified both based on the prepared single FBG and a pair of FBGs. For the fiber laser composed of a pair of FBGs, an output power of 314 W is achieved and the laser performance is stable. In the third chapter, thermal effects in high power fiber lasers are researched based on the thermal conduction equations. For the purpose of figuring out heat dissipation requirements for different parts of the fibers and providing effective cooling ways, the temperature distribution of the active fiber is analyzed through a numerical modeling, and the impacts of different parameters, such as convective heat transfer coefficients, fiber sizes, pump powers and structures, on the fiber temperature are studied. The necessity for thermal management of fiber-to-fiber splice is analyzed in detail, and the concept of thermal contact resistance is introduced to determine the thermal characteristics of a single point. In the fourth chapter, the all-fiber high-power fiber laser oscillator is studied theoretically and experimentally. The model of Yb3+-doped double-clad fiber laser (YDCFL) is built based on steady-state rate equations, and the impact of different parameters, such as cavity mirror reflectivity, active fiber length, pump structure, pump wavelength, and pump power on the laser power is numerically simulated. Different pump structures and wavelengths of all-fiber YDCFL are investigated experimentally. On this basis, a highly efficient all-fiber laser oscillator is designed and realized. An output power of 550 W with a high slope efficiency of 76.4% is realized for a backward pumped all-fiber YDCFL which is pumped by wavelength- locked 976 nm sources. In the last chapter, the all-fiber high-power fiber amplifier is studied theoretically and experimentally. The impact of fiber lengths on laser powers under different pump powers is simulated through a numerical modeling. Theoretical and experimental study is carried out on the thermal properties of passive fiber-to-active fiber splice. Through the introduction of thin copper taper to fix fibers and filling with thermal interface material (TIM) between the fiber and heat sink, the waste heat can be conducted effectively and a good cooling effect can be got. A kilowatt-level Yb3+- doped double-clad fiber amplifier (YDCFA) based on main oscillator power amplifier (MOPA) structure is built experimentally. When the seed power is 160 W and the pump power is 1.22 kW, an amplified laser power of 1.17 kW is realized, and a kilowatt-level all-fiber laser prototype is developed.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15690]
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	范元媛. 全光纤化高功率光纤激光器理论及实验研究[D]. 中国科学院上海光学精密机械研究所. 2012.

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