基于石墨烯/光纤复合波导的3μm高能量超短脉冲光纤激光器关键技术研究

Different from the structure and mode locking mechanism of the saturable absorber, for all-fiber structure, highly damage threshold and full wave bandwidth of mode locking, single mode fiber-multimode fiber-single mode fiber (SMS) have become the focus of the international scientific research. However, the pulse energy is generally not high enough in passively mode locking Er3+: ZBLAN fiber laser based on SMS as limited by the low modulation depth and high mode-locked self-starting threshold. In view of the problems, the project introduce hybrid waveguide G: SMMS-SA (graphene: multicore SMS saturable absorber), which consist of graphene film and graded index two-concentric-core fiber, and the saturable absorption optical properties at 3 μm of G: SMMS-SA will be studied. The nonlinear effect and multimode interference can be controlled by introducing two-concentric-core fiber, graphene film and special index distribution, and the optimization of the saturable absorption optical properties (modulation depth, saturation fluence,etc.) is explored. The mechanisms of high energy dissipative soliton and the evolution of different dissipative solitons based on G: SMMS-SA mode locking at 3 μm will be investigated.

单模-多模-单模光纤波导SMS在结构和锁模机制上不同于传统意义的可饱和吸收材料，因其具有全光纤结构、较高的损伤阈值和全波段的锁模带宽，近几年成为了国际前沿科学研究的热点。然而，由于SMS波导的调制深度较低、锁模自启动阈值较高，大大束缚了高能量锁模光纤激光器的发展。针对此问题，本申请采用石墨烯薄膜与渐变折射率双同芯光纤合成新型石墨烯/光纤复合波导G:SMMS-SA，开展其在3μm波段的可饱和吸收光学特性的研究。通过引入双芯光纤和石墨烯薄膜，优化复合波导的折射率分布，对复合波导的非线性效应和多模干涉进行调控，探索优化复合波导G:SMMS-SA可饱和吸收光学特性（调制深度、饱和通量等）的新方法。揭示基于G:SMMS-SA的3μm波段耗散孤子锁模的形成机制、各耗散孤子态的形成条件及演化过程，实现基于G:SMMS-SA锁模的3μm波段高能量耗散孤子光纤激光器。

基于多模干涉的锁模机制上不同于传统意义的可饱和吸收材料，因其具有全光纤结构、较高的损伤阈值和全波段的锁模带宽，近几年成为了国际前沿科学研究的热点。然而，由于多模干涉锁模的调制深度较低、锁模自启动阈值较高，锁模不稳定等大大束缚了高能量锁模光纤激光器的发展。针对此问题，本申请采用石墨烯薄膜与渐变折射率多模光纤合成新型石墨烯/光纤复合波导 G:SMMS-SA，开展其在3μm波段的可饱和吸收光学特性的研究。通过引入拉锥结构和调节腔外应力，实现了非线性可饱和吸收参数可调谐，找到了优化复合波导G:SMMS-SA可饱和吸收光学特性（调制深度、饱和通量等）的新方法。揭示基于G:SMMS-SA的3μm波段耗散孤子锁模的形成机制、各耗散孤子态的形成条件及演化过程，耗散孤子脉冲宽度可实现19.6ns~55ns可调谐，脉冲能量最大为7.86nJ，中心波长为2960.7nm。