基于色散控制的主动锁模掺镱光纤激光器设计

摘要

设计了一种基于色散控制的相位调制锁模掺镱光纤激光器。针对相位调制锁模中模式跳变现象，基于非线性薛定谔方程，建立了光脉冲在光纤激光器系统中演变的数学模型，通过数值仿真研究了色散对脉冲稳定性的影响。在光纤环形腔中加入光子晶体光纤实现色散补偿，解决了输出脉冲在两个相位差为π的模式间跳变引起的不稳定问题。在稳定锁模的前提下，进一步分析了激光器关键参数（非线性系数、小信号增益系数、调制频率和调制深度）对输出脉冲时域特性的影响。结果表明，在腔内平均色散为－19 ps2／km 时，激光器工作在稳定锁模区域，产生重复频率4．918 GHz，脉宽2．54 ps 的锁模脉冲，这对于后续实验中的优化设计具有指导性意义。%A kind of frequency-modulation mode-locked ytterbium-doped fiber laser is designed.Focused on mode-hopping phenomenon in frequency-modulation mode-locked pattern,the mathematical model of light pulse evolution in fiber laser is established based on nonlinear Schrödinger equation,and the effects of dispersion on the pulse stability are studied through numerical simulation.The mode hopping problem,that output pulses tend to jump back and forth between two modes which are 1 80°apart relative to each other,is solved by employing a photonic crystal fiber in the ring cavity for dispersion compensation.In the premise of stable mode-locking,the effects of several critical parameters (such as the nonlinear coefficient,the small signal gain coefficient,the modulation frequency and the modulation depth)on time-domain characteristics of the output pulses are analyzed.The analytical result shows that the fiber laser works in stable mode-locking region and produces stable output pulses with 2.54 ps pulse width and 4.91 8 GHz repe-tition frequency when the average dispersion is -1 9 ps2 /km.The simulation data play a guiding role in optimal design for the later experiments.