高次谐波混合锁模脉冲生成及其数值仿真研究

High-Order Harmonic Hybrid Mode-Locking Pulse Generation and Its Numerical Simulation Analysis

对混合锁模掺铒光纤激光器中高阶谐波锁模脉冲生成进行了试验和仿真研究。利用非线性偏振旋转技术和碳纳米管可饱和吸收体相结合的混合锁模技术,有效降低谐波脉冲锁模泵浦阈值,更加有利于锁模自启动。通过增加泵浦功率,利用峰值功率钳位和孤子能量量化效应,可实现泵浦功率和脉冲重复频率呈线性关系的谐波锁模脉冲输出。当泵浦功率调节为198.8 mW时,激光器最高输出重复频率约为1.31 GHz,约72阶谐波锁模脉冲,其超模抑制比约为35 dB。同时采用基于修正的非线性薛定谔方程进行了数值模拟,通过调节小信号增益系数为3.4和4.4时,单脉冲分裂为等周期间距的2阶和3阶谐波锁模脉冲,数值仿真结果和试验数据基本相吻合。谐波混合锁模脉冲生成的试验和理论结果有利于进一步了解光纤激光器中谐波脉冲的生成原理和方法。

The generation of high-order harmonic mode-locked pulse in a hybrid mode-locked Erbium-doped fiber laser has been demonstrated in the experiments and simulations.Using the hybrid mode-locking technology including nonlinear polarization rotation technology and carbon nanotube as a saturation absorber in the fiber laser cavity,the pump threshold value can be effectively reduced and the laser is easier to achieve self-starting mode-locking.By increasing the pump power compared with the effect of peak power clamp and soliton energy quantification,a linear relationship between the pump poweruc2p and the pulse frequency repetition rate can be achieved.When the pump power is adjusted to 198.8mW,the laser maximum output repetition rate is about 1.31GHz and about 72-order harmonic mode-locking pulse,its supermode suppression ratio is about 35dB.The modified nonlinear Schrodinger equation is used to validate the experimental procedure.By adjusting the small signal gain coefficient to 3.4and 4.4,the single pulse is splitting into 2and 3-order harmonic mode-locking pulses.The numerical simulation results are consistent with the experimental data.The experimental and theoretical results open the new view to further understand the principle and method of harmonic pulse generation in fiber lasers.