初始啁啾对飞秒脉冲在光子晶体光纤中超连续谱产生的影响

Effect of initial chirp on supercontinuum generation by femtosecond pulse in photonic crystal fibers

采用分步傅里叶方法模拟了初始啁啾对光子晶体光纤中超连续谱产生的影响.根据光纤长度,将光子晶体光纤中脉冲的演化分成初始展宽、剧烈展宽和饱和展宽三个阶段.通过讨论啁啾脉冲和无初始啁啾脉冲在各阶段演化的区别,发现啁啾只在初始展宽和剧烈展宽阶段对光谱有影响,当β2C<0时啁啾有利于光谱的展宽,当β2C>0时则刚好相反,在饱和展宽阶段啁啾不再对光谱产生影响.要想利用啁啾脉冲来获得较宽的光谱,必须选择合适的光纤长度,使输出的脉冲处于剧烈展宽阶段.这为利用啁啾脉冲在光子晶体光纤中获得最佳的超连续谱提供了一定的参考依据.

The numerical simulations with the method of split-step Fourior were presented to investigate the effect of initial chirp on supercontinuum generation in photonie crystal fibers. According to the fiber length, the evolution of pulse in photonic crystal fibers was divided into three stages： initial broadening stage, dramatic broadening stage and saturation broadening stage. By discussing the differences in evolution of the chirp pulse and non-chirp pulse in each stage, we find that the initial chirp only affects the spectrum at the initial broadening stage and the dramatic broadening stage, and the chirp is profitable for spectrum broadening when β2 C 〈 0, but the effect of chirp is the opposite when β2 C 〉 0. In the saturation broadening stage, chirp does not affect the spectrum anymore. If we want to broaden the spectrum by using chirp pulse we must choose a right fiber length, and output the pulse in the dramatic broadening stage. These conclusions provide significant reference for supercontinuum