双零色散光子晶体光纤中超连续谱的产生及控制

 通过数值模拟飞秒脉冲在具有双零色散波长的光子晶体光纤中的传输过程,详细分析了超连续谱的产生和控制机制.结果表明：中心波长处于反常色散区的泵浦脉冲在高阶非线性和高阶色散等作用的调制下,将演化为基孤子和正常色散区的两个色散波|该色散波进而经与之相位匹配的基孤子相干加强而使频谱展宽形成超连续谱,同时两个色散波上出现了干涉引起的振荡现象.进一步对比三种结构的光子晶体光纤中超连续谱的特点,定量分析了两色散波对超连续谱的限制作用,阐述了结构参量对超连续谱的影响.基于上述结论,结合对色散波的中心波长与光子晶体光纤的色散曲线、结构参量之间关系的分析,提出了设计光子晶体光纤的结构来控制超连续谱的方法.作为例证,通过优化光子晶体光纤结构理论上实现了频谱分量覆盖可见光区的平坦超连续谱.

Generation and Control of Supercontinuum in Photonic Crystal Fibers with Two-zero Dispersion Wavelengths

 The generation and control mechanisms of a broadband supercontinuum (SC) in photonic crystal fibers (PCF) with two-zero dispersion wavelengths are demonstrated by simulating the evolution process of a femtosecond pulse numerically.The results reveal that the intrinsic higher-order dispersions and nonlinear effects of PCFs cause the pump pulse,whose center wavelength locates between the anomalous dispersion region,decay into fundamental solitons and two dispersive waves simultaneously.In virtue to the enhancement of the two dispersive waves by their phase-matched solitons,SC will be formed by the two dispersive waves,on which oscillations happen for the interference.Then,the limited effect on the SC applied by the two dispersive waves is analyzed quantitatively by comparing the SCs in three PCFs with different geometrical parameters.Meanwhile,the effects of the geometrical parameters are demonstrated.Based on the above conclusions,considering the analysis on the relationships between the center wavelengths of the dispersive waves and the dispersion curves of PCFs as well as their geometrical parameters,a method to control the range of SC is promoted based on the design of the geometrical parameters.As an example,a flat SC extending to the visible region is achieved by optimizing the geometrical parameter in theory.