低损耗宽带近零色散高非线性光子晶体光纤设计

提出了一种兼具低损耗、宽带近零色散和高非线性的光子晶体光纤结构，该结构光纤包层空气孔直径从纤芯向外层方向渐进增加；应用多极法，通过改变包层空气孔间距Λ、各层空气孔直径和空气孔层数N_r，对光子晶体光纤色散、损耗和非线性特性进行分析，获得了各特性随包层结构参数变化的规律，并最终设计出最佳结构参数。计算结果表明，该结构光纤存在3个零色散点，在1.25～1.55 μm较宽的波长范围内，色散值波动小于0.27 ps·nm?1·km?1，色散斜率小于0.008 ps·km?1·nm?2，1.55 μm波长处损耗为0.021 dB/km，在常用的飞秒激光泵浦波长0.8，1.06，1.55 μm处非线性系数分别达到78.6，60.4，38.2 W?1·km?1。

Design of photonic crystal fibers with low loss broadband near-zero dispersion and high nonlinearity

A photonic crystal fiber (PCF) structure with low loss, broadband near-zero dispersion and high nonlinearity is proposed. The diameter of the air hole in the cladding increases gradually from the core to the cladding. The dispersion, loss and nonlinear characteristics of the PCF are analyzed by the multipole method through changing the air hole spacing, diameter and the number of air hole layers. Finally, the variation law of each characteristic is obtained and the optimal structure parameters of PCF are designed. The results show that the fiber has three zero dispersion points, the dispersion and dispersion slope is less than 0.27 ps·nm?1·km?1 and 0.008 ps·km?1·nm?2 respectively between 1.25 μm and 1.55 μm, and the loss is 0.021 dB/km at 1.55 μm. The nonlinear coefficients are 78.6 W?1·km?1, 60.4 W?1·km?1, and 38.2 W?1·km?1 at the femtosecond laser pumping wavelength 0.8 μm, 1.06 μm and 1.55 μm respectively.