色散平坦渐减光纤中非线性啁啾脉冲的传输及超连续谱的产生

Nonlinear Chirped-pulse Propagation and Supercontinuum Generation in Dispersion-flattened Dispersion-decreasing Fibers

基于非线性薛定谔方程,数值研究了色散平坦渐减光纤中非线性啁啾脉冲的传输及超连续谱的产生。研究结果表明,初始啁啾对脉冲传输及超连续谱产生的影响与泵浦条件和光纤参量的选取有很大关系。当色散平坦渐减光纤具有小的归一化二次色散系数时,适当的正啁啾能显著增强超连续谱的带宽,而负啁啾和太大的正啁啾抑制超连续谱的带宽。能增强超连续谱带宽的正啁啾有一个较宽的范围,但随着输入脉冲孤子阶数的降低,该范围将变窄。当色散平坦渐减光纤具有大的归一化二次色散系数同时输入脉冲为低阶孤子时,初始啁啾对超连续谱带宽的增强效果不明显,初始啁啾接近为0时可产生最宽的超连续谱。

Based on the generalized nonlinear Schrdinger equation,nonlinear chirped-pulse propagation and supercontinuan（ SC） generation in dispersion-flattened dispersion-decreasing fibers（ DFDFs） were investigated numerically. The simulation results indicate that the effect of initial chirp parameter on pulse propagation and SC generation is highly related to the choices of pumping conditions and fiber parameters. When DFDF has small normalized quadratic dispersion coefficient,proper positive chirps can significantly enhance the SC bandwidth,while negative chirps or too large positive chirps suppresses the SC bandwidth. There is a wide range of positive chirps that can enhance the SC bandwidth,but the range of proper positive chirps become narrower as input soliton order decreases; When DFDF has large normalized quadratic dispersion coefficient and the pump pulse is a lower-order soliton,the enhancement of SC bandwidth by initial chirp parameter is insignificant,and the widest SC spectrum is generated when the initial chirp is close to zero.