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题名	新型拉曼光纤激光器及光纤钠导星激光器的研究
作者	张磊
学位类别	博士
答辩日期	2014
授予单位	中国科学院上海光学精密机械研究所
导师	冯衍
关键词	光纤激光器，受激拉曼散射，激光导引星，受激布里渊散射，二次谐波产生，单频激光器，锁模激光器
其他题名	Raman fiber lasers and sodium guide star laser development
中文摘要	高功率光纤激光器在基础研究、工业加工、国防、医疗等领域有着重要应用。近年来，高功率、高亮度稀土掺杂光纤激光器发展迅速，但其发射波长受到稀土离子发射带宽的限制，不能满足一些需要特定波长特殊应用的需求。拉曼激光具有波长灵活的特点，只要有合适的泵浦源，就可以发射增益介质透明波段内任意波长的激光。同时，拉曼光纤激光器的量子亏损低、因而热耗小，所用增益光纤无需稀土离子掺杂、从而其损伤阈值高，增益谱宽且可级联工作等特点，是高功率光纤激光器发展的一个重要方向。本文围绕光纤钠导星激光器应用，对1120nm拉曼光纤激光器、1178nm单频拉曼放大器以及589nm外腔倍频等方面展开理论和实验研究，主要内容包括： 本论文第一章主要介绍了光纤中的受激拉曼散射效应的基本知识，综述了新型拉曼光纤激光器的研究进展，回顾了钠导星激光器的发展历程，指出光纤激光器是钠导星激光发展的一个重要方向。 第二章主要研究了高功率、高效率的1120nm光纤激光器。采用传统拉曼光纤激光器获得大于40W的1120nm激光输出；采用保偏光纤光栅偏振轴交叉对准技术，实现了百瓦级线偏振1120nm掺镱光纤激光器；提出掺镱-拉曼混合放大器的技术路线，从理论上分析其可行性，实验中采用掺镱-拉曼混合放大技术，利用单模保偏光纤获得大于600W的单模线偏振1120nm激光输出；采用掺镱-拉曼混合放大技术，利用20µm芯径的光纤，获得1.3kW的连续1120nm激光输出，该输出功率比目前最高报道的拉曼光纤激光器高了一个数量级；最后从理论上讨论了利用级联拉曼光纤激光器获得千瓦量级1.1µm-2µm之间任意波长激光的可能性。 第三章主要研究了高效率的单频1178nm拉曼光纤放大器。介绍了光纤中的受激布里渊散射效应（SBS），指出其为窄线宽光纤激光器功率提升的主要瓶颈，介绍了常用的SBS抑制方法；搭建基于泵浦-探测原理的SBS增益光谱测试系统，测试了不同光纤的SBS增益谱线，同时研究了SBS增益谱线随应力的变化，这为后续单频光纤放大器实验中的SBS抑制提供了指导；建立单频拉曼光纤放大器的理论模型，采用结构优化和对增益光纤施加纵向应力分布的方法抑制SBS效应；实验中获得了高功率的连续和准连续运转的1178nm单频拉曼光纤激光输出：连续波模式下，最大获得了86W的平均功率输出；准连续波的模式下，最大获得了120W峰值功率输出。 第四章中主要研究了通过二次谐波产生高功率单频的589nm激光。介绍了二次谐波产生的基本原理；采用PPSLT晶体的单通倍频技术获得了7W 589nm单频激光输出；从理论上分析了外腔谐振倍频腔的效率优化方法，实验中利用外腔谐振倍频技术获得了连续和准连续的589nm激光输出：连续波模式下，最大获得了平均功率为53W的钠黄光输出；准连续波模式下，最大获得了峰值功率大于80W的钠黄光输出。利用高精度的波长计，将589nm激光的波长成功锁定于589.1591nm，即钠的D2a线；对1178nm基频光施加了1.71GHz的边频调制，同时通过精确调谐倍频腔的腔长使其自由光谱区为1.71GHz，成功获得了包含D2a和D2b双线的589 nm激光输出。上述提到的589nm激光参数，包括高的输出功率，连续波和准连续波的运转模式，单横模的输出光束质量，单频特性，波长稳定于钠的D2a线以及激光同时包含D2a和D2b的波长分量，使得该激光器成为钠导星应用的理想光源。 第五章主要研究了波长灵活的石墨烯锁模拉曼光纤激光器。利用石墨烯作为可饱和吸收体，受激拉曼效应作为激光增益机制，成功实现了波长为1180nm的锁模拉曼光纤激光器。宽带可饱和吸收体石墨烯同波长灵活的拉曼增益相结合，提供了一种全波段锁模激光输出的技术方案。为了测试石墨烯的可饱和吸收特性，搭建了基于非线性偏振旋转和半导体可饱和吸收镜（SESAM）的全正色散锁模光纤激光器，获得多种形式的皮秒量级的锁模激光输出。这部分的工作为后续的百纳秒脉宽的脉冲钠导星激光器研究提供了前期基础。
英文摘要	High power fiber laser have found applications in scientific research, industrial manufacturing, defense and medical science etc. Recently, rare earth doped fiber lasers with high power and good beam quantity have progressed significantly. However, the laser wavelengths are limited within the emission bands of the rare earth ions, which can not cover lasers that are required by many applications. Stimulated Raman scattering (SRS) effect is featured with wavelength versatility. Fiber laser using Raman as gain mechanism could emit arbitrary wavelength within the gain medium’s transmission spectrum, providing an appropriate pump laser. Meanwhile, Raman fiber laser has advantages of high quantum efficiency, wide gain spectrum and high damage threshold. With the goal of developing laser for laser guide star, high power 1120nm Raman fiber laser, 1178nm single frequency Raman fiber amplifier and 589nm second harmonic generation are investigated theoretically and experimentally in the thesis. In Chapter I, we first introduce the SRS effect in fiber. Then, the development of the high power Raman fiber laser and single frequency Raman fiber laser are reviewed systematically. At last, we summarize the history of guide star laser development and point out that Raman fiber laser based 589nm laser is one important candidate for the new generation of sodium guide star laser. In Chapter II, 1120nm fiber laser with high power and high efficiency is researched, which is the ideal Raman pump laser for the following 1178nm single frequency Raman fiber amplifier. First, over 40W linearly-polarized 1120nm laser is achieved with a conventional Raman fiber laser. Then, with polarization maintaining (PM) Yb-doped fiber, a 100W fiber laser at 1120nm is achieved. Third, an integrated Ytterbium-Raman fiber amplifier (YRFA) is proposed and the simulation results show good potential for 1120nm laser power scaling. In the experiment, over 600W true single-mode, linearly-polarized laser at 1120nm is generated. Further power scaling is realized with a fiber laser system with core diameter of 20µm. 1.3 kW 1120nm laser is achieved, which is an order of magnitude higher than what have been reported for Raman fiber lasers so far. Our simulation shows that the proposed YRFA architecture offers a prospect of achieving kilowatt-level Raman fiber lasers covering the whole spectral range from 1.1 µm and 2 µm by seeding a kilowatt Yb-doped fiber MOPA with a multiple-wavelength laser. In Chapter III, single frequency 1178nm Raman fiber amplifier is studied. We first introduce the stimulated Brillouin scattering (SBS) effect in fiber and the techniques for SBS suppression. Then a SBS gain spectrum measurement setup based on the pump-probe method is built and we succeed in measuring the SBS gain spectrum of different fiber and fiber with different applied strain distributions, which provides a meaningful information for the study of SBS suppression in single frequency Raman fiber laser. In the single frequency Raman fiber amplifier experiment, multi-stage fiber amplifier architecture and longitudinally applied strain distribution onto the gain fiber are adopted to suppress the SBS effect. CW and QCW single frequency 1178nm laser with output power of up to 80 and 120W is achieved, respectively. In Chapter IV, second harmonic generation (SHG) of the 1178 nm laser is studied. We first introduce the basic concept of the SHG process. A maximum 7W 589nm laser is achieved with a PPSLT single pass SHG operation. Resonant cavity SHG technique is applied to increase the conversion efficiency. The cavity parameters are optimized to increase the SHG efficiency according to numerical simulations. In CW mode, a maximum 53W 589nm single frequency, single mode laser is generated. In QCW mode, the peak power of the 589nm laser reaches over 80W. With the help of a highly precise wavelength meter, the laser is frequency-stabilized to 589.1591nm, which is the D2a line of the sodium absorption. Moreover, by phase modulating the 1178nm seed laser and adjusting the free spectral range of the SHG cavity to 1.71GHz, the 589nm laser emits at the D2a and D2b line simultaneously. All the above laser characteristics, including high output power, single transverse mode, single frequency, frequency-locking to D2a and the coexistence of re-pumping line, make the laser a perfect source for laser guide star. In Chapter V, wavelength-versatile mode-locked Raman fiber laser is studied. A mode-locked 1180nm fiber laser with graphene as the saturable absorber and SRS as the gain mechanism is demonstrated. The combination of Raman gain and the graphene-based ultra-wide bandwidth saturable absorber offers a prospect of real wavelength-versatile mode-locked laser source. For testing the modulation depth of graphene, we build several kinds of all normal dispersion mode-locked fiber laser with tens of picosecond pulse width.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15897]
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	张磊. 新型拉曼光纤激光器及光纤钠导星激光器的研究[D]. 中国科学院上海光学精密机械研究所. 2014.

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