光子晶体光纤耦合器中的标量调制不稳定性

从光纤耦合器的耦合模方程出发，用偶奇超模对其进行重写，讨论了当输入条件使奇偶超模其中之一被单独激发时，在光子晶体光纤耦合器中的调制不稳定性.结果表明：光子晶体光纤耦合器中在正常和反常色散区均存在调制不稳定性，并且调制不稳定性与三阶色散项无关、与四阶色散项有关，给出了增益谱在不同色散区随输入功率的变化关系；当满足一定条件时，在光子晶体光纤耦合器中传播的准连续波可以分解成脉冲序列，由此可以分离和提取超短脉冲.关键词：光子晶体光纤耦合器偶次超模奇次超模标量调制不稳定性

Scalar modulation instability in photonic crystal fiber couplers

The nonlinear coupled-mode equations are rewritten by even and odd modes. We study modulation instability of photonic crystal fiber couplers when either even or odd mode is launched alone. The result shows that there are new types of modulation instability in both the normal and the anomalous-dispersion regimes. Modulation instability is related with four phase dispersion and has no relation with three phase dispersion. The gain spectra have been given as function of input power in various dispersion regimes. Quasi-cw can be changed into pulse array under certain conditions, and we can extract super-short pulses from it.