饱和非线性下零色散附近的交叉相位调制非稳

从光纤中扩展的耦合非线性薛定谔方程组出发,在饱和非线性光纤零色散附近,研究了不同二、四阶色散参量下交叉相位调制不稳定性增益谱及其临界扰动频率、谱宽和谱峰随两光波入射功率的演化特点.研究表明,随色散参量不同,增益谱随两光波入射功率的增大可能出现三种演化形式：一是始终是两个分离的谱区;二是由开始时的两个合成一个,最后再分离成两个;三是始终是一个谱区.饱和非线性的存在则使每个谱区的谱宽、谱峰及远离零点的临界扰动频率,随两光波入射功率的增大可能呈现出先增大后减小的特点,使第二谱区靠近零点的临界扰动频率呈现先减小后增大的特点,从而可能出现两个不同的输入功率对应同一个增益峰值和谱宽的情形.色散参量对增益谱的谱峰影响小,对谱宽影响大.越靠近零色散区,每个谱区谱宽越大,越易连成一个谱区.

Cross-phase Modulation Instability in Vicinity of Zero Dispersion Regions in Case of Saturable Nonlinearity

Starting from the extended coupled nonlinear Schrdinger equations in optical fibers,the evolutions of the gain spectra of cross-phase modulation instability and their corresponding critical perturbation frequencies,spectral widths,and the peak gains with the input powers of the two optical waves were investigated for different parameters of the second- and fourth-order dispersions in the vicinity of zero dispersion regions in optical fibers with saturable nonlinearity.The results show that,depending on different dispersion parameters,the gain spectra evolve with the input powers of the two optical waves in three ways.The first,there are always two separated spectral regions.The second,the two spectral regions may link together and turn into one region at first,and split into two ones again finally.The third,there is always only one spectral region.The saturable nonlinearity will make spectral width,the peak gain,and the critical perturbation frequency which is far away from the zero point,increase with the input powers before decrease for every spectral region,and make the critical perturbation frequency which is close to the zero point,decreases with the input powers before increase for the second spectrum.Thus,it means that,a unique value of peak gain and spectral width may correspond to two different input powers.And,the dispersion parameters influence the peak gain of spectra slightly.But,they can influence considerably the spectral widths.The closer to the zero dispersion regions the optical waves are,the wider every spectrum is and the easier it is for the two spectra to link together and turn into one.