时分复制技术皮秒脉冲光纤放大器数值研究

Numerical Study on Picosecond Pulse Fiber Amplifier Based on Divided-Pulse Amplification Technique

基于时分复制脉冲放大的理论模型,数值研究了五级双折射晶体组级联时分复制光纤放大系统中各参数对皮秒放大脉冲特性的影响。结果表明,子脉冲之间非线性相移积累的不同会导致耦合效率降低。当时分复制后子脉冲间距大于2.5倍脉宽时,子脉冲串耦合效率达到最优。在光纤放大器非线性系数和最大增益一定的条件下,为获得峰值功率为10 MW的变换极限皮秒放大脉冲,给出了种子脉冲峰值功率和增益光纤长度的选择范围。在光纤长度确定的条件下,为了降低晶体偏转角和透射率对放大脉冲性能的影响,应选择低峰值功率的种子脉冲和高增益的光纤。

Based on the theoretical model of divided-pulse amplification, the effect of all parameters in the divided pulse fiber amplification system with five-step birefringent crystals group cascading on the property of amplified picosecond pulse is numerically investigated. The results indicate that, the difference of nonlinear phase shift accumulation between divided pulses leads to the reduction of the combining efficiency. The optimal combining efficiency is obtained when the time separation between two adjacent divided pulses is larger than 2.5 times of pulse width. Under the condition of nonlinear coefficient and maximum gain of fiber amplifiers being fixed, the selection ranges of gain fiber length and seed pulse peak power are presented in order to obtain a transform-limited amplified pulse with an output peak power of 10 MW. Under the condition of fiber length being fixed, it is suggested to choose a seed pulse with low peak power and a fiber with large gain in order to suppress the impact of rotation angle bias and transmissivity on the property of the amplified pulse.