| 题名 | 短脉冲光纤激光及其放大技术研究 |
| 作者 | 邹峰 |
| 文献子类 | 博士 |
| 导师 | 周军 |
| 关键词 | 光纤激光器 Fiber laser 超短脉冲 ultra short pulse 被动锁模 passive mode locking 主振荡-放大 master oscillator power amplifier 光子晶体光纤 photonic crystal fiber |
| 其他题名 | Study on Short Pulse Fiber Laser and its Amplification Techniques |
| 英文摘要 | 短脉冲激光在工业加工、医学诊疗、光电对抗以及科学研究等领域有着广阔的应用前景。与固体激光器相比，光纤激光器具有光束质量好、转换效率高、热管理方便、可全光纤化以及结构紧凑等诸多优点，随着近年来高功率抽运技术的改进和新型大模场面积双包层光纤以及光子晶体光纤（PCF）的出现，高功率脉冲光纤激光器和放大器的性能不断提升，是国际上激光技术领域的研究热点之一。本文针对数纳秒量级脉宽与皮秒量级脉宽两类短脉冲激光，进行了短脉冲光纤激光的产生与高功率放大的理论与实验研究，论文主要研究内容与所取得的成果包括以下几个方面： 首先介绍了获得纳秒级脉冲光纤激光输出的两种主要技术途径——基于主动或被动调Q的脉冲光纤激光器和基于半导体种子激光调制的脉冲主振荡功率放大（MOPA）光纤激光器，并对脉冲电调制半导体激光种子源产生纳秒脉冲进行了重点介绍。在超短脉冲方面，综述了被动锁模光纤激光器的研究进展，并从光纤锁模脉冲演变特性入手，讨论了孤子、展宽脉冲、自相似脉冲和全正色散脉冲四种锁模机制。最后介绍了实现高功率超短脉冲光纤放大的几种技术方案。 开展了小型化纳秒脉冲光纤激光器的实验研究。出于小型紧凑化结构设计与脉冲参数灵活可调的目的，采用了以脉冲电调制半导体激光器为种子光源、以光纤放大器进行功率放大的全光纤化脉冲MOPA技术方案。研究表明电调制分布反馈式（DFB）半导体激光器种子结合双程光纤放大的结构能够有效加强小信号放大能力，并获得高光谱信噪比和窄线宽的激光输出。基于此方案，在1 μm波段实现了最高峰值功率为15 kW的窄线宽激光输出，脉冲宽度为3.06 ns，重复频率10-50 kHz可调；在1.5 μm波段，利用两级光纤放大实现了峰值功率为20 kW的激光输出，脉冲宽度为5 ns，重复频率35-50 kHz可调，并完成了小型化工程样机。 设计并实现了稳定的1 μm波段超短脉冲锁模光纤激光器，获得了宽可调谐范围的耗散孤子锁模输出。在实验上研究了线性腔半导体可饱和吸收镜（SESAM）锁模并着重研究其束缚态锁模现象，通过调节泵浦详细分析了不同束缚态锁模的输出光谱、自相关迹的特点，研究了束缚态锁模的形成与演变规律来揭示其内在物理机制。为了获得线性大啁啾脉冲，进一步实验研究了耗散孤子锁模激光器，该锁模激光器采用全保偏光纤，仅调节两个环路内的抽运功率就可自启动非线性放大环形镜（NALM）耗散孤子锁模。同时利用可调谐滤波器，在调谐激射波长的同时滤波形成耗散孤子。最大波长调谐范围为1015-1080 nm，输出脉冲宽度在7.86-17.8 ps范围内变化，但是激光器输出脉冲峰值功率始终钳制在50 W以内。 进行了高平均功率超短脉冲光纤放大技术的研究，实现了输出平均功率达300 W的超短脉冲激光放大输出。首先，分析得出自相位调制（SPM）、受激拉曼散射（SRS）和光纤端面损伤是高功率超短脉冲光纤放大的瓶颈，其中在光纤啁啾脉冲放大系统中SPM是首要限制因素。为进一步突破光纤非线性的限制，基于第三章所研究的全保偏1030 nm SESAM种子源，分别采用自研大模场双包层光纤与超大模场棒状光子晶体光纤进行高功率放大。其中采用自研55/400 μm（纤芯NA=0.04）超大模场光纤的全光纤化放大系统获得了平均功率为206 W的超短脉冲激光输出，研究了放大激光的光谱展宽现象。采用棒状大模场光子晶体光纤进行功率放大，输出平均功率达到300 W，对应的峰值功率为422 kW，有效抑制了非线性效应并保持了高光束质量的激光输出。 开展了光子晶体光纤啁啾脉冲放大的理论和实验研究。首先理论分析补偿脉冲色散所需的光栅间距，其次基于大线性啁啾的NALM耗散孤子锁模种子源和光子晶体光纤放大级，搭建了啁啾脉冲光纤放大系统。通过单模正色散展宽脉冲后经光子晶体光纤放大，最后由多层电介质光栅对压缩脉冲，获得了平均功率15.7 W，脉冲宽度1.4 ps的超短脉冲输出，光栅对压缩效率达到92.3%。实验研究表明放大过程中积累的SPM会严重影响压缩脉冲波形的质量，通过控制预放级中积累的SPM则可以进一步将脉宽压缩到900 fs。; Short pulse laser has extensive applications in industrial processing, medical diagnosis and treatment, photoelectric confrontation and scientific research and other fields. Compared with solid-state lasers, fiber lasers have many advantages such as good beam quality, high conversion efficiency, easy heat management, all-fiber and compact structure. With the improvement of high-power pumping technology and new large-mode-aera double-clad fiber and photonic crystal fiber (PCF), the performance of high-power pulsed fiber lasers and amplifiers continues to increase, and fiber laser is one of the hotspots in the field of laser technology. In this paper, the theoretical and experimental research on the generation and high power amplification of short pulsed fiber laser are carried out for two kinds of short pulse lasers with several nanosecond pulse width and picosecond order pulse width. The main contents and achievements of this paper include the following aspects: Firstly, two main technical approaches to obtain the laser output of nanosecond pulse fiber are introduced. The pulsed MOPA fiber laser based on active or passive Q-switched pulsed fiber laser and semiconductor-based laser modulation is used to generate nanosecond pulse laser. Then the research progress of passive mode-locked fiber lasers is introduced in terms of ultrashort pulse. As for the characteristics of fiber-mode-mode pulse evolution, four kinds of modelocking mechanisms are discussed, such as soliton, broadened pulse, self-similar pulse and all-normal-dispersion. Finally, several fiber amplification technical schemes to realize high power ultra short pulses are introduced. Experimental study on miniaturized nanosecond pulsed fiber lasers was carried out. For the purpose of compact of laser and flexibility of pulses’ parameters, the MOPA scheme is employed, which is featured with pulsed electrical modulation on LD and all-fiber structure amplification. The results show that the DFB seed combined with the double-pass amplification structure can effectively enhance the small signal amplification and obtain the high signal-to-noise ratio and the narrow linewidth output. Based on this scheme, a narrow linewidth output with a maximum peak power of 15 kW is achieved in 1 μm band with pulsewidth of 3.06 ns and a repetition rate of 10-50 kHz. In the 1.5 μm band, the peak power of 20 kW is realized by two-stage amplification, the pulse width is 5 ns, the repetition frequency is 35-50 kHz, and the miniaturized engineering prototype is completed. A stable 1 μm ultrashort pulse mode-locked fiber laser is designed and implemented, and a wide-tunable range of dissipative soliton mode-locked lasers is obtained. Experimrntally, the SESAM mode locking with linear cavity was studied. Especially, the characteristics of the output spectrum and autocorrelation traces of different bind-state mode locking were analyzed in detail by adjusting the pump, and the formation and evolutionary law of the binding states were studied. Its intrinsic physical mechanism was revealed. In order to obtain the linear-chirp pulse, the dissipative soliton mode-locked laser was studied experimentally. The mode-locked fiber laser adopted polarization maintaining fiber and only adjusted the pumping power in the two loops to start the NALM dissipative solitons. A tunable filter was used to tune lasing wavelength as well as filter out the dissipative solitons. The maximum wavelength tuning range is 1015-1080 nm and the output pulse width varies from 7.86 to 17.8 ps, but the pulses’ output pulse peak power is always within 50 W. The study of the high-average-power ultra-short-pulse fiber amplification technology was carried and an ultra-short-pulse laser with average output power of 300 W was obtained. Firstly, it was concluded that the self-phase modulation (SPM), the stimulated Raman scattering (SRS) and the fiber end-face damage are the bottlenecks of the high power ultra-short-pulse fiber amplification, in which SPM is the primary limiting factor in the fiber chirped pulse amplification system. In order to further break through the limitation of fiber nonlinearity, based on the 1030-nm SESAM seed source studied in Chapter 3, high-power amplifications were carried out by using self-made double-clad LMA fiber and large-mode-area rod photonic crystal fiber. In this paper, the ultra-short-pulse laser with 206 W output was obtained with all-fiber structure by using 55/400-μm LMA fiber (core NA = 0.04) and the spectral broadening is studied. Rod-type PCF amplifier’s output power is 300 W and the corresponding peak power is 422 kW, which effectively suppressed the nonlinear effect and maintained good high beam quality. The theoretical and experimental study on the chirped pulse amplification of PCF was carried out. First, the gratings’ spacing required for compensating pulse dispersion was analyzed theoretically. Secondly, based on NALM dissipative soliton with large linear chirped and PCF amplifying stage, a chirped pulsed fiber amplification system was constructed. Finally, the ultra-short pulse output with average power of 15.7 W and pulse width of 1.4 ps is obtained by the multi-layer dielectric grating compressor, and the compression efficiency is 92.3%. Experimental results show that the SPM accumulated during the amplification process will seriously affect the quality of the compressed pulses’ waveform. By controlling the SPM accumulated in the pre-stage, the pulse width can be further compressed to 900 fs. |
| 学科主题 | 光学工程 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/30977]  |
| 专题 | 中国科学院上海光学精密机械研究所 |
| 作者单位 | 中国科学院上海光学精密机械研究所 |
| 推荐引用方式 GB/T 7714 | 邹峰. 短脉冲光纤激光及其放大技术研究[D]. |
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