保偏光纤中在不同频率区域拉曼效应和参量放大增益谱

Raman effect on parametric amplification gain spectra of different frequency propagation regimes in polarization maintaining fibers

根据考虑拉曼效应后的双折射光纤所满足的非线性相干耦合薛定谔方程,推导出了当沿两个偏振轴入射两束不同波长的激光脉冲时所产生的增益表达式.通过与入射相同频率的光脉冲所产生增益的对比,在考虑拉曼效应的情况下,讨论了入射不同频率光脉冲对增益谱的影响.结果表明,在正常色散区和反常色散区,当输入两束激光脉冲频率不同时,增益谱较输入相同频率激光脉冲时产生了明显的变化,其外侧的斯托克斯部分和反斯托克斯部分增益峰,随着群速度失配的增加强度明显加强、偏离中心频率,可以用于提取太赫兹脉冲.当两偏振模处于不同色散区时,增益谱与不考虑拉曼效应时也存在明显的不同,增益谱的对称性遭到破坏,斯托克斯部分的增益峰强度要明显高于反斯托克斯部分.

The expression of gain is derived from nonlinear Schr6dinger equation with consideration of raman effect when two laser pulseswith different wavelengths are emitted into birefringence fiber along two polarization axes. The gain characteristic input laser pulsesof different frequencies are revealed by comparing the laser pulses of identical frequency. The result show that the gain spectra will apparently differ when input laser pulses have different frequencies in normal dispersion regime and anomalous dispersion regime. The intensities of outboard gain peak about stokes part and anti-stokes part increase and frequency deviates from central frequency as group velocity mismatch increases. Therefore, the THz pulse can be extracted. The gain spectrum will be apparently different from that with no Raman effect taken into account, when the two polarization modes, are in different dispersion regimes. The symmetry of gain spectrum will be damaged. The intensity of gain peak of stokes is apparently stronger than the peak of anti-stoke.