基于宇称-时间对称的锁模光纤激光器机理研究

Mode-locked fiber lasers with low threshold, tunable pulse duration and spectrum width have great application prospects in micro-fabrication, information processing and medicine. However, the coupling loss between devices in fiber lasers raises the mode-locking threshold and tunability of pulse duration and spectrum width. The highly focused frontier issue — the mode-locked fiber lasers based on parity-time symmetry — utilize the balance mechanism of gain and loss, which can both reduce the mode-locking threshold and achieve the tunability of pulse duration and spectrum width. The fiber lasers are not involved in the relevant research..We intend to introduce parity-time symmetry into fiber lasers, and focus on the issues of mode-locked mechanism and pulse characteristics. The contents are as follows:.1) Study the parity-time symmetric mode-locking mechanism to reveal the modulation rules of parity-time symmetric devices on pulses..2) The mode-locking threshold equation and pulse tracing model will be constructed to master the modulation disciplines of gain and loss of parity-time symmetry on mode-locking threshold, pulse duration and spectrum width..3) Realize the parity-time symmetric mode-locked fiber laser with low threshold, tunable pulse duration and spectrum width based on the modulation rules of parity-time symmetry..The results of the project will have significant scientific and practical value for enriching the theory of mode-locked fiber lasers and realizing the new ultrafast fiber laser.

低锁模阈值、脉宽和光谱可调谐的锁模光纤激光器在微加工、信息处理和医学等领域具有巨大的应用前景。然而光纤激光器器件的耦合损耗提高了锁模阈值，并减小了脉宽和光谱的调谐范围。基于宇称-时间对称的锁模激光器采用增益和损耗平衡机制利用腔内损耗，在降低锁模阈值的同时实现了脉宽和光谱的可调谐，是目前国际上高度关注的前沿课题，但相关研究未涉及光纤激光器。.本项目拟将宇称-时间对称引入光纤激光器领域，针对其锁模机理、脉冲特性调控机制等问题开展如下研究：.1）研究宇称-时间锁模机制，揭示宇称-时间对称器件对脉冲的调控规律。.2）构建锁模阈值方程和脉冲追踪模型，掌握宇称-时间对称的增益和损耗对锁模阈值、脉宽和光谱的调控规律。.3）基于宇称-时间对称的调控规律，实现低锁模阈值、脉宽和光谱可调宇称-时间对称锁模光纤激光器。.项目成果将对丰富锁模光纤激光器理论，实现新型超短脉冲光纤激光器具有重要的科学意义和实用价值。

超短脉冲锁模光纤激光器在在大容量光通信、超精细加工、量子信息、超分辨显微成像等领域具有广泛的应用价值。但其在实际应用中受制于光纤器件的耦合损耗，提高了锁模阈值，减小了脉宽和光谱的调谐范围等问题，因此，如何设计出具有低锁模阈值、脉宽和光谱可调谐的锁模光纤激光器是目前激光器领域亟需解决的科学问题。. 针对以上科学问题，本项目基于宇称-时间对称的锁模激光器，根据锁模的离散耦合模方程组理论，通过数值求解研究了正常色散与零色散时PT对称和PT对称破缺状态下的锁模条件；在此基础上分析了PT对称锁模光纤激光器中色散对锁模动力学的影响，并搭建了环形腔PT对称锁模光纤激光器。采用增益和损耗平衡机制，利用腔内损耗，研究了宇称-时间锁模机制，揭示了宇称-时间对称器件对脉冲的调控规律，在降低锁模阈值的同时实现了脉宽和光谱的可调谐；构建了锁模阈值方程和脉冲追踪模型，根据宇称-时间对称的增益和损耗，摸清了锁模阈值、脉宽和光谱的调控规律；最终实现了低锁模阈值、脉宽和光谱可调宇称-时间对称锁模光纤激光器。. 本项目丰富了锁模光纤激光器理论，实现了新型超短脉冲光纤激光器，对锁模光纤激光器在超大容量光通信、超精细加工、量子信息、超分辨显微成像等领域的研究和应用具有重要的科学指导意义和实际应用价值。

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