三五阶非线性下啁啾超高斯脉冲的啁啾和频谱

利用三五阶非线性效应下的扩展非线性薛定谔方程,在忽略光纤色散的情况下,计算模拟了以二阶情形为例的啁啾超高斯光脉冲的啁啾和频谱。结果表明,脉冲无预啁啾时,正五阶非线性增大啁啾量,负五阶非线性在减小啁啾量的同时还改变啁啾曲线的形状。当预啁啾与五阶非线性系数同(异)号时,总啁啾增加(减小)。随着超高斯脉冲阶次的增大,总啁啾量增大,脉冲中心附近无啁啾的范围变宽,整个有啁啾的范围变小,总啁啾中预啁啾所占比重增大。脉冲无预啁啾时,正负五阶非线性分别可以增大和减小频谱展宽。预啁啾若增强非线性所致啁啾,则可能使频谱峰值结构加强,谱峰数目增多。当超高斯光脉冲的阶次或最大非线性相移增大时,在某些宽大的频谱峰上还可能出现许多精细谱峰。

Frequency Chirps and Spectra of Chirped Super-gaussian Optical Pulses Propagating in Optical Fibers with Cubic-quintic Nonlinearity

Utilizing the extended nonlinear Schrdinger equation including cubicquintic nonlinearity and neglecting the dispersion of optical fibers,the frequency chirps and the power spectra of chirped Super-Gaussian optical pulses are calculated and simulated by taking the second order Super-Gaussian optical pulses for example.The results show that,for the unchirped optical pulses,the positive quintic nonlinearity increases the chirps while as the negative one decreases the chirps and changes the chirp shape as well.When the initial chirp of the pulse is of same(opposite) sign as that of quintic nonlinearity coefficient,the whole chirp increases(decreases).With the increase of the order of the SuperGaussian pulse,the whole chirp increases and the range of the central region where the chirp is nearly zero becomes wider while the whole chirp range narrower. And the proportion of the initial chirp to the whole one increases.For the unchirped pulses,the positive and negative quintic nonlinearity can increase and decrease the spectral broadening,respectively.For the chirped pulse,if the initial chirp enhances the nonlinearity caused chirp,the oscillatory structure of the spectra may be enhanced and the peak number may increase.In addition,when the order of the Super-Gaussian pulse or the maximum nonlinear phase shift increases,this case may occurs that,many fine spectral peaks may appear on some wider spectral peaks.