2μm高能量时域宽调谐方波脉冲源研究

Thulium-doped pulsed fiber lasers at 2μm have attracted considerable interests as novel laser sources, due to their wide applications in the fields of remote sensing, eye-safe lidar, laser medical system, optoelectronic countermeasure and special material processing. It is very difficult to achieve high-energy laser pulse directly by using of conventional fiber laser technology, which limits their practical applications. In this project, wide tunable in the temporal domain and wave-breaking-free high energy rectangular pulse will be achieved by graphene saturable absorber-based passively mode-locked thulium-doped fiber laser at 2μm wavelength operating in the dissipative soliton resonance (DSR) region. Firstly, the DSR phenomenon in a mode-locked thulium-doped fiber using graphene saturable absorber is investigated experimentally and theoretically, and the shaping mechanism and the pulse characteristics influenced by cavity parameters are analyzed. Then, stable rectangular pulse at 2μm with energy of 100nJ and pulse-width tunable from 10ns to 100ns will be achieved. Finally, the transmission and amplification characteristics of this rectangular pulse and its applications for supercontinuum generation will be investigated. These results in the project may benefit our understanding of DSR phenomenon and rectangular pulse generation in a passively mode-locked fiber laser, provide helpful theoretical and experimental fundamentals for the in-depth study of new high-energy pulsed lasers.

2μm掺铥脉冲光纤激光器在遥感、人眼安全雷达、激光医疗、光电对抗和特殊材料加工等领域具有重要应用，近年来成为新型光纤激光源研究的热点。采用传统的光纤激光技术很难直接获得高能量的2μm激光脉冲，这限制了其应用。本项目拟通过工作在耗散孤子共振（DSR）区的基于石墨烯的被动锁模掺铥光纤激光器，获得高能量、脉宽可调、无光波分裂的2μm矩形激光脉冲。对石墨烯被动锁模掺铥光纤激光器中的DSR现象进行理论和实验研究，分析其产生机理以及激光腔的各项参数对输出脉冲物理特性的影响；实现2μm波段单脉冲能量100nJ、脉宽10-100ns可调的稳定矩形脉冲输出；研究这种矩形脉冲的传输和放大特性，以及在超连续谱产生中的应用。本项目的完成，将有助于深入了解被动锁模光纤激光器中的DSR现象和矩形脉冲产生，为进一步研究新型高能量脉冲激光器提供有益的理论及实验基础。

高能量方波脉冲在信号处理系统、光纤传感、高功率激光器打孔等领域有着重要应用，而利用被动锁模光纤激光器产生方波脉冲具有多种优势。本项目基于耗散孤子共振（DSR）理论，对采用不同被动锁模机制、工作在不同波段的光纤激光器进行了研究，获得了高能量时域宽调谐无波分裂的方波脉冲。利用谱方法和分步傅里叶方法求解复立方-五次方金兹堡-朗道方程和耦合非线性薛定谔方程，研究了基于DSR的方波脉冲的形成机制和影响因素。研究了将石墨烯等新型二维材料转移到光纤端面的问题，获得了质量良好的锁模器。研究了工作在DSR区的NPR被动锁模掺镱光纤激光器，实现了脉宽为812ns的稳定方波输出；通过改变腔长获得了最大脉宽分别为431ns和164ns的稳定方波脉冲。研究了工作在DSR区的NOLM被动锁模掺镱光纤激光器，实现了方波脉冲的多稳态输出，验证了偏振对方波脉冲的影响；实现了中心波长在1039.2~1070.8nm可调谐的稳定方波脉冲输出。研究了工作在DSR区的NALM被动锁模掺镱光纤激光器，实现了重复频率为401.60kHz、脉宽在18~90ns可调、单脉冲能量在1~8nJ可调的稳定方波脉冲输出。研究了工作在DSR区的低重复频率全正色散NOLM被动锁模光纤激光器，实现了重复频率为133.18kHz的方波脉冲输出，最大时域宽度为762ns，最大单脉冲能量为60nJ。研究了工作在DSR区的超低重复频率L波段NOLM被动锁模掺铒光纤激光器，实现了重复率低至48.48kHz的稳定方波脉冲输出，最大时域宽度为574ns，最大单脉冲能量为170nJ。研究了工作在DSR区的被动锁模掺铥光纤激光器，实现了稳定的2μm波段方波脉冲输出，最大时域宽度80ns，最大单脉冲能量126nJ；选择适当的方波脉冲作为种子光，研究了方波脉冲的放大稳定性。本项目的完成，可为进一步研究新型高能量锁模光纤激光器提供有益的理论及实验基础，吸引科研人员研究和探索基于新型锁模器的高能量激光脉冲的新现象和新机理，并在高能量脉冲的极端非线性科学问题上获得新认识。