基于光子晶体光纤的高斯脉冲光谱压缩数值研究

Study on spectral compression of Gaussian pulse in photonic crystal fibers

为了获得高质量的窄线宽光脉冲,采用单模光纤和光子晶体光纤相结合的光谱压缩技术,通过分步傅里叶变换方法求解非线性薛定谔方程,数值模拟了1550nm波段高斯脉冲光谱压缩过程。结果表明,当初始脉冲的脉宽、峰值功率及所采用光子晶体光纤的参量一定时,光谱压缩存在一最佳光子晶体光纤长度;且初始光脉冲的峰值功率越大,所采用光子晶体光纤的非线性系数越大,所需光子晶体光纤最佳长度越短,所得谱压缩比越大;利用最佳长度为4.152m的光子晶体光纤对峰值功率为110W、初始脉宽为0.65ps的高斯脉冲进行光谱压缩时,可得谱压缩比为3.47的最佳谱压缩光脉冲;脉冲形状对光谱压缩产生一定的影响,高斯脉冲较超高斯脉冲光谱压缩效果更好。该研究结果对研制窄线宽、超短脉冲光纤激光器具有指导意义。

In order to get high quality pulse with narrow linewidth, spectral compression of Gaussian pulse was investigated numerically by solving the nonlinear Schrodinger equation. It was found that, when the Gaussian pulse with the central wavelength of 1550nm successively propagated in a single-nlode fiber and a photonic crystal fiber, its spectra would be compressed. Further more, when input peak power, pulse width of Gaussian pulse, and nonlinear coefficient of photonic crystal fibers were fixed, there would exist an optimal photonic crystal fiber length. If peak power of the initial light pulse was the greater, nonlinear coefficients of photonic crystal fiber was the larger, the optimal length of photonic crystal fiber was the shorter, the compression ratio of spectra was the greater. The highest spectral compression ratio of 3.47 was achieved for the Gaussian pulse with the input peak power of 110W and the initial pulse width of 0.65ps, while the optimum length of photonic crystal fibers was only 4. 152m. The spectral compression of Gaussian pulse was better than super Gaussian pulse under the same simulation condition because of the pulse shape. The results would provide a significant guidance for making the ultrashort pulse fiber laser with narrow linewidth.