利用多极法对包层空气孔为正六边形对称结构光子晶体光纤的模式场进行了分析,计算出不同波长下基模的有效折射率,结合使用模式耦合理论和传输矩阵法对基于光子晶体光纤的布拉格光栅特性进行了计算和仿真,对比了常规单模光纤所成光栅与相同光栅周期的光子晶体光纤布拉格光栅反射谱及时延特性之间的差异。在此基础上,对光纤光栅的切趾特性进行了研究,选择不同的切趾函数,得出最佳切趾函数下光栅传输谱。理论计算和仿真结果表明,随波长增加,基模有效折射率下降,光栅谐振波长出现蓝移,采用啁啾化处理后,10 cm 长光子晶体光纤光栅可以提供1 200 ps 以上的线性时延。

The mode field of photonic crystal fiber structured with hexagon symmetry hole cladding was analyzed by multipole method, and the effective indexes of base mode of different wave length were got. The characteristics of this photonic crystal fiber grating were computed and simulated by coupled-mode method and transmission matrix method. Moreover, the differences were compared between conventional fiber grating and photonic crystal fiber grating on their reflection spectrum and delay. The apodization characters of this fiber grating were also researched to get optimal apodization function and corresponding transmission spectra. Compared with the conventional fiber grating, it is found that the refractive index of core mode declines as wavelength rising, and photonic crystal fiber grating show a clear blue shift. When chirp processed, 10 centimeter-long photonic crystal fiber grating can provide 1 200 ps linear delay.