基于微腔滤波和四波混频锁模的高重频超快光纤激光研究

High-repetition-rate mode-locked fiber laser has important applications in fields of optical communication, optical frequency comb, and precision frequency metrology, and is the hot research area of nonlinear optics and ultrafast optics. Due to the confinement of conventional mode-locking method and fiber devices, the repetition rate of pulses in passively mode-locked fiber laser is relatively low. The main purpose of this project is to combine the ultrafast laser and fiber microcavity for crossover study, investigate the manner and mechanism of periodic interaction between optical wave and microcavity in the highly-nonlinear strong-filtering system, and realize high-repetition-rate mode-locked fiber laser based on microcavity filtering and four-wave mixing. To achieve these, following major studies will be carried out: (1) Designing and manufacturing highly-nonlinear narrow-linewidth multi-channel microcavity filters, exploring the behavior and mechanism of the nonlinear interaction between optical wave and microcavity; (2) Establishing the physical model and mathematical equation of the microcavity-mode-locked fiber laser, interpreting the principle of mode locking based on microcavity filtering and four-wave mixing, investigating the formation, interaction, and dynamic evolution of the high-repetition-rate pulses; (3) Utilizing the novel mode-locking method and optimizing the laser system to achieve highly-stable high-repetition-rate (larger than 200 GHz) mode-locked pulses. The obtained results can not only help to reveal phenomenon and mechanism of nonlinear interplay between optical wave and microcavity, but also provide high-repetition-rate ultrashort pulse sources for major national science and engineering as well as defense science and technology.

高重频锁模光纤激光在光通信、光频梳、精密光谱测量等方面具有重要应用价值，是非线性光学和超快光学的热点研究领域。受传统锁模方法和器件的限制，被动锁模光纤激光器中脉冲的重频较低。本项目旨在结合超快激光与光纤微腔进行交叉研究，探索高非线性、强滤波系统中光波与微腔周期性作用的方式和机理，实现基于微腔滤波和四波混频锁模的高重频光纤激光系统。拟开展研究主要有：①设计并制备高非线性、窄线宽、多通道的微腔滤波器，探索光波与微腔非线性相互作用的方式和机理；②建立微腔锁模光纤激光器的物理模型和数理方程，阐释微腔滤波和四波混频实现锁模的原理，研究高重频脉冲的形成、相互作用及动态演化过程；③利用新方法进行锁模并优化光纤激光系统，实现高稳定性、高重频（>200 GHz）锁模脉冲输出。研究成果不仅有助于揭示光波与微腔非线性相互作用的现象和机理，同时可以为国家重大科学工程和国防科技等领域提供高重频超短脉冲光源。

高重频锁模光纤激光系统在光纤通信、传感、精密物理测量等领域具有重要的应用前景，如何获得低成本、高稳定的高重频激光脉冲是基础领域和工业应用的研究热点之一。本项目以微结构光纤器件和高非线性纳米材料为基础，研究高重频超快光纤激光的形成机理和演化特性，探索其在光开关、光纤传感、矢量涡旋光场产生等方面的应用。项目开展的主要研究内容包括：(1)提出了制备微纳拉锥光纤、光纤微腔和D型光纤的方法，研究了微结构光纤的形状、尺寸等参数与其光学特性之间的关系，为开展后续研究提供了基础；(2)结合非线性薛定谔方程和光谱滤波函数，研究了光纤激光器中色散、非线性效应对高重频脉冲传输的影响，揭示了高重频脉冲的演化机理，所得模拟结果对该类实验研究具有指导作用；(3)利用液相剥离法制备了多种低维纳米材料，分别获得了基于聚合物薄膜和D型光纤的可饱和吸收体，实现了包括高重频谐波锁模、单脉冲锁模的多种运转方式。由于D型光纤上纳米材料单位面积承受的光强较小，该类可饱和吸收体损伤阈值极高，所得激光脉冲具有平均功率大、重复频率高等优点；(4)基于少模光纤中的模式转换机理，利用拉锥光纤、错位熔接等技术实现了一种超快矢量光场激光器，输出光场同时具有超短脉冲和空间结构光场的优势，在粒子操纵、时空孤子、频率转换等领域具有重要的应用前景。该项目培养研究生4名，发表SCI论文26篇，其中本项目为第一标注2区论文3篇，3区1篇；本项目为第二标注的1区论文2篇，2区论文3篇，3区论文2篇。相关论文被SCI引用300余次，1篇论文入选“中国百篇最具影响国际论文”和ESI“热点论文”，被评为“陕西省优秀自然科学学术论文”，3篇论文入选ESI“高被引论文”。