色散管理光纤锁模激光器在近零色散域的非线性优化

目前，飞秒激光脉冲因脉冲宽度窄和峰值功率高的特点被广泛运用在多种领域中。其中，色散管理光纤锁模激光器因其特有的腔内呼吸机制使输出的激光脉冲能量更高，光谱更宽、脉宽更窄。使用啁啾布拉格光纤光栅进行色散管理的光纤锁模激光器能够实现真正的全光纤结构，提升激光器的紧凑性和稳定性，因此基于啁啾布拉格光纤光栅进行色散管理的光纤锁模激光器具有更加实际的应用意义。采用数值模拟的方法，研究了基于啁啾布拉格光纤光栅进行色散管理的掺镱光纤锁模激光器中单模光纤在腔内的不同分布对脉冲动力学过程和输出脉冲参数的影响。系统分析了谐振腔内净色散值不同时，腔内单模光纤的分布对脉冲在腔内的动力学过程的影响。模拟结果表明，在腔内净色散值为负时，啁啾布拉格光纤光栅与增益光纤间的单模光纤越短，光纤激光器维持稳定单脉冲运行的最大泵浦强度更高且输出光谱更宽，从而能够获得脉宽更窄的去啁啾脉冲；腔内净色散值越接近零时，啁啾布拉格光纤光栅与增益光纤间的单模光纤长度对输出脉冲参数作用的影响越显著；腔内净色散值为正时，单模光纤在腔内的分布对输出脉冲影响逐渐减弱，优化单模光纤分布提升锁模激光器性能并不明显。最后，提出了一种通过改变单模光纤在腔内的分布来提高激光器输出性能的优化方法。

Nonlinearity optimization of dispersion-managed mode-locked Yb-doped fiber lasers with near-zero net cavity dispersion

Femtosecond laser pulses are widely used in many fields due to their narrow pulse width and high peak power. The dispersion-managed fiber mode-locked laser has higher pulse energy, wider spectrum and narrower pulse due to its unique in-cavity breathing mechanism. The fiber mode-locked laser using chirped Bragg grating for dispersion management can realize the real all-fiber structure and improve the compactness and stability of the laser. Therefore, the fiber mode-locked laser using chirped Bragg grating for dispersion management has more practical significance. The effects of different distribution of single-mode fiber in ytterbium-doped fiber mode-locked laser based on chirped fiber Bragg grating on pulse dynamics and output pulse parameters are studied by numerical simulation. The influence of the distribution of single-mode fiber on the dynamic process of pulse in the cavity is analyzed when the net dispersion is different. The simulation results show that when the net cavity dispersion is negative, the shorter the single-mode fiber between the chirped fiber Bragg grating and the gain fiber, the higher the pumping threshold and the wider the output spectrum of the fiber laser can maintain the stable monopulsing operation, so that the narrow pulse width can be obtained. When the net cavity dispersion is close to zero, the effect of the length of single mode fiber between the chirped fiber Bragg grating and the gain fiber on the output pulse parameters is more significant. When the net cavity dispersion is positive, the influence of the single mode fiber distribution in the cavity on the output pulse gradually weakens, and the performance of the mode-locked laser is not significantly improved by optimizing the single-mode fiber distribution. Finally, an optimization method is proposed to improve the output performance of the laser by changing the distribution of single mode fiber in the cavity.