双余弦相位调制对超高斯脉冲的频谱压缩

Spectral Compression of Super-Gaussian Pulse by Dual Cosinoidal Phase Modulation

针对具有非线性负啁啾的超高斯脉冲,提出了一种双余弦相位调制方法,采用该方法对高非线性光纤中超高斯脉冲的频谱压缩进行优化。结果表明:由于初始超高斯脉冲的非线性负啁啾与非线性光纤中自相位调制引起的正啁啾失配导致时间相位不平坦,频谱出现分裂和旁瓣,压缩质量受限。通过对超高斯脉冲进行外部的两个余弦相位补偿调制可以减少频谱旁瓣的产生,延长频谱压缩距离,提高频谱压缩质量;其中这两个余弦相位调制的振幅和频率来自于对超高斯脉冲的非线性相移分析;在大范围展宽因子下,超高斯脉冲的频谱压缩质量也可以优化。

A dual cosinoidal phase modulation method is proposed to improve spectrum compression of the super- Gaussian pulse with nonlinear chirp in a highly nonlinear fiber. The results show that the temporal unlevel phase of the super-Gaussian pulse resulting from the mismatch between the initial nonlinear negative chirp and the nonlinear positive chirp that induced by self-phase modulation can give rise to the spectrum splitting and residual sidelobes, which degenerates the quality of spectral compression. Phase compensation by external dual cosinoidal phase modulation can effectively reduce the residual sidelobes in the spectrum and extend the distance of spectral compression, so that the quality of the spectrum compression can be enhanced. And the amplitudes and frequencies of the dual cosinoidal phase modulation originate from the nonlinear phaseshift analysis for the pulse. Also, the quality of spectrum compression in a wide range of the initial stretching factor can be optimized.