基于MOPA结构的200W纳秒脉冲光纤激光器研究

200 W NANOSECOND PULSED FIBER LASER BASED ON MOPA STRUCTURE

文垚

11749254

硕士

物理电子学

张新海

2019-05-24

2019-07-12

哈尔滨工业大学

深圳

大功率光纤激光器作为目前工业3D制造加工的重要产品，特别是在增材加工中已经是不可或缺的部件。在率光纤激光器中，脉冲光纤激光器已经是目前科研研究的重点。脉冲主振荡功率放大光纤激光器（MOPA）由于其光束质量好、单脉冲能量大、平均功率高等优点在激光加工领域、医疗健康领域、武器制造、空间光通信领域都有着非常广阔的前景。在目前研究工作中，MOPA结构的光纤激光器在输出光功率、脉冲能量仍有进一步研究的空间。在激光放大的过程中光纤激光器产生的自发放大辐射效应（ASE）、非线性效应（Non-Linear Effect）以及热效应都是阻碍脉冲光纤激光器发展的原因。因此，基于以上研究背景下，本课题基于MOPA 脉冲光纤激光系统展开相关研究，课题首先制作一台激光器，然后通过研究光纤激光器放大过程中产生的自发放大辐射和非线性效应，并且研究如何抑制这些效应从而提高平均功率，最终提高系统的光脉冲峰值功率和光束质量，输出纳秒脉冲激光。本文主要做的工作如下：（1）绪论首先介绍了光纤激光器研究的背景，以及该论文研究200 W纳秒脉冲光纤激光器的意义。并且研究了国内外关于纳秒脉冲光纤激光器的相关文献，对于光纤激光器如何产生纳秒脉冲进行了相关的总结。 （2）第二章主要以脉冲光纤器的相关知识做出阐述，首先介绍了光纤激光器的基本理论部分，其次介绍了行波放大技术理论、增益光纤模式特性、非线性效应理论研究以及其他影响光纤激光器的因素。（3）第三章主要详细阐述了基于MOPA纳秒脉冲光纤激光器的关键技术。这部分首先介绍了脉冲光纤激光器工作原理，以及针对光纤激光器中的泵浦耦合技术展开了讨论，还阐述了目前高功率光纤激光器常用的双包层光纤，最后介绍了光纤合束技术的研究现状。（4）最后的实验部分为：对于MOPA结构的高功率纳秒脉冲光纤激光器进行了实验设计，采用种子源+两级级联放大的结构。整个激光器主要由调制半导体激光种子源和一级单模单包层掺镱光纤（10 μm / 125 μm）放大器，以及二级大模场面积掺镱光纤（30 μm / 250 μm）组成。半导体激光种子源的光谱中心波长为1064 nm，调制之后的激光脉冲宽度为可调谐的，范围从10 ns - 350 ns，重复频率在200 kHz - 1500 kHz范围内可调。激光器采用风冷结构，当半导体激光种子源调制重复频率为200 kHz，脉冲宽度为350 ns时，种子光被一级单包层掺镱光纤放大器放大经过第二级放大结构最后输出为680 mW，经过二级放大后最后输出201.7 W，放大之后光谱中没有出现明显的放大自发辐射现象。 关键词：纳秒脉冲；光纤激光器；主振荡功率放大；高功率

As an important product of industrial 3D manufacturing, high power fiber laser has become an indispensable component in material addition processing. Pulsed fiber lasers are the focus of current research in rate fiber lasers. Pulsed Master Oscillation Power Amplified Fiber Laser (MOPA) has broad prospects in the fields of laser processing, medical and health, weapon manufacturing and space optical communication due to its good beam quality, large single pulse energy and high average power. At present, there is still room for further research on the output optical power and pulse energy of MOPA fiber laser. In the process of laser amplification, the spontaneous emission effect (ASE), non-linear effect and thermal effect produced by fiber laser are all the reasons that hinder the development of pulsed fiber laser. Therefore, based on the above research background, this topic carries out related research on MOPA pulsed fiber laser system. Firstly, we make a laser. Then we study the spontaneous emission and non-linear effects in the amplification process of the fiber laser, and how to suppress these effects so as to improve the average power. Finally, the peak power and beam quality of the system are improved, and nanosecond pulsed laser is output. The main work of this paper is as follows:(1) The introduction firstly introduces the background of the research on fiber laser and the significance of the research on 200 W nanosecond pulsed fiber laser. The related literatures about nanosecond pulsed fiber lasers at home and abroad are studied, and how to generate nanosecond pulses in fiber lasers is summarized.(2) Chapter 2 mainly elaborates on the relevant knowledge of pulsed fiber lasers. Firstly, the basic theory of fiber lasers is introduced. Secondly, the theory of traveling wave amplification, the mode characteristics of gain fiber, the theory of non-linear effect and other factors affecting fiber lasers are introduced.(3) In Chapter 3, the key technologies of MOPA nanosecond pulsed fiber laser are described in detail. In this part, firstly, the working principle of pulsed fiber laser is introduced, and the pump coupling technology in fiber laser is discussed. Then, the double cladding fiber commonly used in high power fiber laser is described. Finally, the research status of fiber bunching technology is introduced.(4) The last part of the experiment is the experimental design of a high power nanosecond pulsed fiber laser with MOPA structure. The structure of seed source and two-stage cascade amplification is adopted. The laser consists of a modulated semiconductor laser seed source, a single mode single clad Ytterbium-doped fiber amplifier (10 μm/125 μm) and a two-stage large mode area Ytterbium-doped fiber (30 μm/250 μm). The spectral center wavelength of the semiconductor laser seed source is 1064 nm. After modulation, the laser pulse width can be tuned, ranging from 10 ns to 350 ns, and the repetition frequency can be tuned in the range of 200 kHz to 1500 kHz. When the repetition rate of laser seed source modulation is 200 kHz and the pulse width is 350 ns, the seed light is amplified by a single clad Ytterbium-doped fiber amplifier at first stage, and the output is 680 mW after the second stage amplification, and 201.7 W after the second stage amplification. After amplification, there is no obvious phenomenon of amplified spontaneous emission in the spectrum.Keywords: Nanosecond Pulse, Fiber Laser; Main Oscillation Power Amplification, High Power

拓扑近藤绝缘体 近藤崩溃 变程跳跃 磁性掺杂 反常霍尔效应 磁输运

topological kondo insulator Kondo break down variable range hopping magnetic doping Anomalous Hall Effect mganetotransport

中文

联合培养

南方科技大学

文垚. 基于MOPA结构的200W纳秒脉冲光纤激光器研究[D]. 深圳. 哈尔滨工业大学,2019.