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题名	高亮度光纤激光合成技术理论与实验研究
作者	杨依枫
学位类别	博士
答辩日期	2015
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	光纤激光器 光反馈环形腔 被动相干合成 光谱合成 多层电介质反射式衍射光栅
其他题名	Study on high brightness beam combining technology of fiber lasers and amplifiers
中文摘要	自半导体激光泵浦技术和双包层光纤问世以来，光纤激光技术发展迅速，广泛应用于各领域。与常规全固态激光器相比，光纤激光器具有转换效率高、光束质量好、热管理方便、结构紧凑等优点，在民用和国防领域获得了很大的发展。然而，由于介质的非线性效应、光纤端面损伤和热致光致损伤等物理因素的制约，单根光纤激光器的输出功率存在理论极限。目前，单模单纤光纤激光的最高输出功率纪录已达到 20 kW，但功率的进一步提升变得非常困难。基于光纤激光阵列的合成技术是一种有效突破单纤输出功率极限并获得高亮度激光的方法，近年来成为全固态激光技术领域的研究前沿。基于全光反馈环形腔的被动相干合成技术结构简单，方便设计与集成，并且采用光学滤波的形式，无需复杂的主动相位控制，受到了持续关注。光谱合成是高亮度光纤激光合成技术的另一个重要技术手段。光谱合成对光纤激光光源的相位没有要求，光谱线宽要求低，同时合成光以单孔径输出，合理设计光栅参数可以使合成系统达到几十千瓦输出功率，具有深远的发展前景。 本论文首先对光纤激光器，合成技术以及光纤激光合成在各领域的应用现状进行了简要回顾。工业和国防领域的重大需求牵引为光纤激光器合成技术的快速发展提供了源源动力。 对基于全光反馈环形腔的被动相干合成系统进行了系统的分析与实验。建立了全光反馈环形腔被动相位锁定的理论模型，对合成效率、阵列规模扩展性和系统工作状况等进行了理论分析与研判。在理论模型的指导下，搭建了二维阵列排布的光纤激光器阵列全光反馈环形腔被动相位锁定系统，采用7路光纤放大器阵列的合成达到了2.2 kW的相干合成输出，采用4路光纤放大器阵列的合成达到了5.4 kW的相干合成输出。同时，对系统的功率稳定性、光谱特性和光束质量进行了分析，并探究了相位噪声对全光反馈环形腔被动相干合成效果的影响。 在完成高功率被动相干合成实验的同时，也将一系列新技术、新器件引入全光反馈环形腔被动相干合成系统中，解决了其固有缺陷。将注入锁定激光器引入被动相干合成系统中作为自开关主振荡，在提升合成系统安全性的同时优化了相位锁定效果。同时，也将衍射光学元件引入连续波与脉冲波全光反馈环形腔被动相干合成系统中作为空间滤波器件。采用自制的1×3达曼光栅作为空间滤波器，搭建了三路掺镱光纤激光器阵列全光反馈环形腔被动相干合成实验平台，实现了20 W连续波输出、相干条纹对比度88.7%的相干合成原理验证实验，同时实现了三路平铺孔径9.6 ns，2.208 MHz脉冲的相干合成，合成光峰值功率达到1.02 kW，相干条纹对比度达到82.9%。新技术的探索实验证明了被动相干合成系统的稳定性和相位锁定效果两方面的提升潜力。 对光纤激光光谱合成技术进行了初步探索。光谱合成技术因具有单孔径输出和高合成效率的重要优势，成为合成技术前景最为光明的方案。本文基于自主研制的偏振非相关多层电介质反射式衍射光栅，搭建了50 W量级无偏振近衍射极限超荧光源阵列，实现了4光束阵列平均功率 214 W ，合成效率94.7%的光谱合成原理验证系统，合成光光束质量My2=1.5，Mx2=3.7。进一步搭建高功率光谱合成实验平台与高功率光束动态评估系统，实现了6光束阵列总输出功率7.09 kW，合成效率83%的光谱合成。同时详细研究了影响合成效率与合成光光束质量的因素，为下一步实现更高功率、更优光束质量的光谱合成奠定了坚实的基础。
英文摘要	Thanks to the birth of laser diode and double cladding fiber, fiber laser has been widely used in many field. Compared with the traditional all solid-state laser, fiber laser has the advantage of high conversion efficiency, excellent beam quality, convenient heat management and compact structure, which has experienced a great development in the field of industry and military. The power record for near-diffraction limited from a single fiber amplifier is 20 kW. However, a single fiber laser appears unlikely to approach powers greater than 100 kW due to thermal aberrations, nonlinearities and optical or thermal damage. The beam combining technology has the capability to scale fiber lasers to higher power levels and maintain good beam quality, which provides a potential solution to overcome these limits. Passive coherent beam combining (CBC) with an all-optical feedback loop is simple in design and operation, and does not require complex active feedback, which has experienced a continuous improvement in recent years. Spectral beam combining (SBC) has an advantage of single aperture output and low require in beamlets phase, which becomes a most promising scheme among the beam combining technologies. This paper starts from an overview of the development of fiber laser, all kinds of beam combining technologies such as incoherent and coherent beam combining, and its actual application in industrial processes. Significant demand led to the rapid development of fiber laser and beam combining technology in recent years. The passive CBC system based on the all-optical feedback loop is studied theoretically and experimentally. By establishing a two-dimension passive phase locked compound ring cavity resonator, a total power of 2.2 kW with an array of 7 Yb-doped fiber amplifiers and a total output power of 5.4 kW with an array of 4 elements is proposed. Power stability, spectrum characteristic, beam quality and the effects of phase noise on phase locking is studied. A series of new technology and optical components is introduced into the passive CBC based on all-optical feedback loop to solve its inherent defects. An injection-locked fiber laser is used to promote the safety of the amplifier chains and improve the visibility of the far-field pattern. We find that the phase-locked far-field interference pattern of our system with seed laser extinguished is stable, and the visibility is up to 91.5%. Diffractive optical element is used as an intracavity spatial filter in passive phase locking of both the continuous-wave and pulsed fiber amplifiers array. We demonstrate a proof-of-principle experiment on the performance of an all-optical feedback loop in passive CBC of three Yb-doped fiber amplifiers with 1×3 Dammann grating spatial filter. By using this diffractive-optics-based spatial filtering technique, the phase locked far-field visibility of it is up to 88.7% at 20 W continuous wave CBC. Three tile-aperture nanosecond fiber laser is also phase-locked with a peak power of 1.02 kW. Single aperture output and high combining efficiency provides a group of advantage of SBC technology, which is the most hopeful scheme to achieve 100 kW level. By establishing a high power SBC platform and beam quality evaluation system, 7.09 kW spectral beam combining with 83% combining efficiency and a beam quality of four times the diffraction limit is achieved by home-made non-polarized multilayer dielectric reflection grating. Factors affecting the combining efficiency and the combined beam quality are also studied in detail, which show a brilliant prospect of SBC to a higher power level and a better beam quality.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15912]
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	杨依枫. 高亮度光纤激光合成技术理论与实验研究[D]. 中国科学院上海光学精密机械研究所. 2015.

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