负五阶非线性下预啁啾高斯光脉冲的啁啾和频谱

为探究光纤负五阶非线性和光脉冲预啁啾对高斯光脉冲频率啁啾和频谱的综合影响,在忽略光纤色散的情况下,利用包含三五阶非线性的扩展非线性薛定谔方程,计算和分析了啁啾高斯脉冲的频谱和总啁啾。结果表明,脉冲无预啁啾时,负五阶非线性的存在可使脉冲频率啁啾的形状由单“S”形变为双“S”形,并使脉冲的中心附近由正啁啾变为负啁啾。此外,负五阶非线性的存在使预啁啾对脉冲频谱的影响发生了较大的变化。预啁啾与非线性所致啁啾叠加后对脉冲频谱的谱峰数目影响较小,而对能量在各个谱峰上的分布影响较大,在某些最大非线性相移下,甚至会出现总啁啾减小使谱峰值数目增加的情况。该研究对光开关、光脉冲压缩以及光纤通信系统等领域的深入发展具有一定的指导意义。

Frequency Chirps and Spectra of Chirped Gaussian Optical Pulses in Case of Negative Quintic Nonlinearity

The purpose of the paper is to study the synthetic effects of the negative quintic nonlinearity of optical fibers and the initial frequency chirps of optical pulses on the frequency chirps and spectra of Gaussian optical pulses. Utilizing the extended nonlinear Schrdinger equation including quintic nonlinearity and neglecting the chromatic dispersion of optical fibers, the frequency spectra and the whole chirps of chirped Gaussian optical pulses are calculated and analyzed. The results show that, when the pulses are initially unchirped, the negative quintic nonlinearity can make the shapes of chirps change from single 'S' to dual 'S'shape and even make the chirps in the central regions of pulses change from positive to negative. In addition, the negative quintic nonlinearity can also make the effects of initial chirps on spectra of pulses change considerably. After overlapping with the chirps caused by nonlinearity, the initial chirps can greatly influence on the energy distribution among the spectral peaks while slightly influence on the number of peaks. For some values of maximum nonlinear phase shifts, it may even occur that, the decrease of the whole chirps makes the number of spectral peaks increase. This investigation will contribute theoretically to the deep development of the optical switching, pulse compression, optical fiber communications, and so on, to some degrees.