石墨烯锁模耗散孤子光纤激光器动力学特性研究

The generation of ultra-short pulses with high energy is very useful in a variety of applications including studying and observing the transient structural changes of the microscopic material on their physical, chemical or biological characteristics, etc. Higher energy ultra-short pulse can be formed in dissipative soliton lasers, while graphene as a laser mode locker has many merits such as ultra-fast recovery time, higher optical damage threshold, and lower saturation intensity and so on. In this study, we will investigate how the graphene thickness affects the operational patterns of the mode-locked fiber lasers, and discuss the unusual dynamics of dissipative solitons. We will first use monolayer graphene as the SA to obtain self-similar pulse with broader spectra and higher pulse energy in dissipative soliton lasers, and offer the parameters for obtaining high-energy ultra-short pulses. Since the multilayer graphene has an exceptionally high nonlinear response, we will study the rogue waves with huge peak power, and discuss how to form and control rouge wave in an all normal dispersion mode-locked fiber lasers based on multilayer graphene SA. Further more, since the graphene absorbance is independent of frequency, we will also study wavelength-tunable passively harmonically mode-locked fiber lasers with ultrashort pulses and a high repetition rate, and offer an operational mechanism for these fiber lasers. The above study will develop the theory for using mode-locked lasers as platform to produce dissipative solitons, reveal their unusual dynamics, and indicate the relationship between the thickness and characteristics of the graphene. It will also provide the key technology for obtaining the new ultra-short femtosecond pulse source, and lay a good theoretical and experimental foundation for the research on dynamic patterns in mode-locked fiber lasers based on saturable absorber.

高能量超短脉冲光源在研究微观物质世界物理、化学和生物的瞬态结构变化等领域具有重要应用。耗散孤子激光器可产生高能量光脉冲，石墨烯饱和吸收体具有超快恢复时间、高光损伤阈值、低饱和强度等优点。本项目拟将石墨烯厚度与锁模激光器工作模式相结合，研究耗散系统中脉冲的动力学过程。采用单层石墨烯做饱和吸收体，在耗散孤子激光器中产生高能量、宽带自相似超短光脉冲，探讨获得高能量超短光脉冲的条件；利用多层石墨烯具有较大非线性系数的特性，在全正色散耗散孤子激光器中，产生超大峰值功率奇异波光脉冲，探明影响奇异波形成的关键因素；利用石墨烯独立于波长的饱和吸收特性，实现波长可调谐高重复频率光脉冲稳定输出，研究其形成机理。本课题将发展利用光纤锁模激光器研究非线性耗散动力学系统的平台，揭示石墨烯厚度与其特性的关系，提供构造新型飞秒光源的关键技术，为基于饱和吸收体锁模光纤激光器动力学特性的研究奠定良好的理论和实验基础。

耗散孤子激光器可产生高能量光脉冲，可调谐耗散孤子激光器具有重要应用。激光器产生光脉冲的关键器件为可饱和吸收体，而实现可调谐的关键器件为滤波器。本项目从饱和吸收体的制备与表征出发，辅以研制全光纤型光谱滤波器元件，进而研究耗散系统中脉冲的动力学过程。具体研究内容如下：分别制备、表征了单层率大于90%的单层石墨烯薄膜及3-7层的多层石墨烯薄膜，研制了基于锥纤倏逝场及三明治结构等两种不同类型石墨烯锁模器件；研究了石墨烯锁模高能量宽带自相似脉冲光纤激光器，得到了脉冲光谱带宽为186.6 nm，去啁啾脉冲宽度为22.5 fs，去啁啾脉冲峰值功率为1.26 MW的放大自相似光脉冲源；优化设计了耗散孤子激光器，得到了脉宽为11 ps，去啁啾后脉宽为44 fs，单脉冲能量为66 nJ，脉冲峰值功率为1.5 MW的输出光脉冲；研制了石墨烯高阶谐波锁模孤子光纤激光器，实现了61阶高阶谐波、重复频率为603.9 MHz 光脉冲输出；制作了基于锥纤的波长可调谐衰减器及波长间隔精确可控的梳状干涉滤波器；研制了波长可调谐、单层石墨烯锁模耗散孤子光纤激光器，实现了中心波长从1559.77 nm到1556.25 nm之间连续可调；研制了L波段可调谐光纤锁模激光器，实现了中心波长从1583.0到1602.4 nm范围内连续可调；深入分析了耗散孤子光纤激光器中奇异波形成机理，得到了能量高达50 nJ的奇异波光脉冲。另外，本项目还研制了波长间隔精确可控的多波长掺镱及掺铒光纤激光器；研制了高阶谐波暗脉冲光纤激光器及放大器、爆发模式耗散孤子光纤激光器及放大器、耗散孤子方脉冲光纤激光器等新型光纤激光系统。通过本项目研究，掌握了研制高性能、耗散孤子激光光源的关键技术。为新型、稳定、高能量、性能灵活可控光纤激光光源的研制提供了一些启示。为基于饱和吸收体和光谱滤波器的光纤激光器动力学特性的研究奠定了良好的理论和实验基础。