LD抽运大能量Nd：YLF绿光激光器特性研究
文献类型：学位论文
| 作者 | 杨琦 |
| 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 | 朱小磊 |
| 关键词 | 板条放大器 电光调Q 热效应分析 腔外倍频 Nd：YLF Nd：LiLuF4 LBO |
| 其他题名 | Research on LD pumped high energy Nd:YLF green laser |
| 中文摘要 | 全固态高能量绿光激光器在科学研究、工业、医疗、军事等众多领域都有着广泛的应用。尤其在水下通信领域，对高能绿光激光器有着强烈的需求。本论文的重点就是围绕着水下激光通信对激光-光源的需求，开展研究了一台波长区别于532 nm的高能量全固态绿光器，以实现双通道水下通信的应用要求。研究内容主要包括Nd：YLF激光振荡器，Nd：YLF板条放大器以及腔外倍频器。 论文首先介绍了高能量全固态绿光激光器的应用背景和发展现状，介绍了Nd：YLF晶体的特性和研究进展以及常用的倍频晶体。论文综述了涉及高能量绿光激光器的基本理论，包括放大理论，热效应分析和倍频理论。 为了确定高能量1047 nm MOPA系统的技术方案，论文研究过程中尝试了端面泵浦的Nd：YLF振荡器，侧面泵浦的Nd：YLF振荡器和端面泵浦的Nd：LiLuF4作为系统的前端振荡器。通过分析比较，我们最终确定端面泵浦的Nd：YLF振荡器作为MOPA系统前端的技术方案。研究工作首先利用端面泵浦的Nd：YLF振荡器技术，获得了脉宽为13.7 ns，能量为15 mJ近衍射极限光束质量的调Q激光脉冲输出。 论文工作以理论分析为指导，实验研究了影响Nd：YLF激光放大器输出的几个重要因素，具体包括：寄生振荡、泵浦光的耦合与匀化、存储效率等。研究过程中，自主设计了放大器的冷却和泵浦结构，自主设计了用于泵浦光耦合匀化的梯形波导棱镜。最终运用四级板条放大器，在重复频率为50 Hz的情况下，成功实现了单脉冲能量840 mJ的基波1047 nm激光脉冲序列输出，整个激光器MOPA系统的光-光转化效率为12.5%。输出激光的脉冲宽度为9.13 ns，对应的最大峰值功率达到93 MW。测试结果显示，放大后的激光脉冲光斑光强分布较均匀，强度空间分布呈现了非高斯型分布，其光束质量因子测试值为Mx2=3.26，My2=4.29。研究工作最后利用非线性晶体LBO，通过腔外倍频的方式实现了520 mJ的523.5 nm绿光输出，倍频效率高达62%。 论文研究工作在深入研究LD侧面抽运Nd：YLF板条MOPA系统1047 nm波长的放大特性基础上，进一步开展了Nd:YLF板条MOPA系统针对1053 nm波长的放大特性研究工作。首先，通过LD双端抽运电光调QNd:YLF振荡器获得了单脉冲能量为16 mJ的1053 nm基波信号光。为了增大Nd:YLF板条激光放大器的光-光转换效率，MOPA系统的预放大器采用了双程放大结构，信号光通过四级放大后，获得了655 mJ的能量输出，光束质量为Mx2=7.0，My2=4.6。利用LBO晶体进行腔外倍频，获得了单脉冲能量为400 mJ的527 nm绿光脉冲输出，倍频效率达到了61%。 |
| 英文摘要 | All-solid-state high energy green lasers have widely used in scientific research, industry, medical, military and other fields. Especially in underwater communication, it is desired demanded for a high energy green laser. In this thesis, we carried out reaserch on the all-solid-state high energy green laser, which the wavelength is distinguished from the 532 nm, for the purpose of releasingapplication requirements of the two-channel underwater communication. Our research mainly included Nd: YLF oscillator, Nd:YLF slab amplifier and extra-cavity frequency doubling. In this thesis, we reviewed the application background and development status of all-solid-state green laser, introduced the character of Nd: YLF and the normal frequency doubling crystal. The fundamental theory of high energy green laser is presented, including laser amplification, thermal analysis and frequency doubling. We tried the end-pumped Nd: YLF oscillator, side-pumped Nd: YLF oscillator, end-pumped Nd: LiLuF4 oscillator as the choice of seed laser of the MOPA system. By comparison, we determined to use the end-pumped Nd: YLF oscillator as the master oscillator of the system. The dual end-pumped Nd：YLF oscillator provided Q-swithed output energy of 15 mJ with pulse duration of 13.7 ns. Accoring to the instruction of the theoretical analysis, we researched the influence factors of the amplifier by experimental test. The influence factors included parasitic oscillation, coupling and homogenization of the pump light, storage efficiency and so on. We designed pumping and cooling structure of the amplifier ahead and the trapezoid waveguide for coupling the pump laser. By four stage amplification, at the repetition rate of 50 Hz, the system provided output energy of 840 mJ at the wavelength of 1047 nm. The total optical conversation effiency of the system was 12.5%. The amplified pulse width duration was 9.1 ns, its peak power was around 93 MW. The far-field beam intensity distribution was well-distributed but became non-Gaussian in shape. On the condition of 840 mJ pulse energy output, the beam quality factors of Mx2=3.26, My2=4.29. A LBO crystal was used for the extra-cavity frequency doubling. The maximum pulse energy of 520 mJ was obtained. The frequency conversation was up to 62%. On the basis of researching amplification character of the LD side-pumped 1047 nm Nd: YLF MOPA system. We also researched on the 1053 nm Nd: YLF high energy MOPA system. By utilizing anend-pumped EO Q-switched oscillator, 16 mJ 1053 nm Q-switched pulse energy was achieved. We used double-pass pre-amplifiers to increase the extraction effiency of slab amplifier.We got the maximum output energy of 655 mJ at 1053 nm with the beam quality of Mx2=7.0, My2=4.6. When a nonlinear crystal LBO was used for extra-cavity frequency doubling, more than 400 mJ of 527 nm green laser was generated, the conversion effiency was up to 61%. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15911]  |
| 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 | 杨琦. LD抽运大能量Nd：YLF绿光激光器特性研究[D]. 中国科学院上海光学精密机械研究所. 2015. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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