利用有限元方法对纤芯中心带有一个微小空气孔的光子晶体光纤进行了分析, 得到了其模场分布、损耗及色散特性随光纤结构参数及波长的变化规律. 根据光的衍射原理及光子晶体光纤的传输特性, 对空气孔传光的物理本质进行了解释. 得到了微小空气孔低损耗、高强度、单模传输时, 光子晶体光纤结构参数及波长的取值范围. 设计出了一种优化的光子晶体光纤结构, 其模场很好地集中在纤芯微小空气孔中, 限制损耗α=5.9× 10-5 dB/km, 为微小空气孔传光的光子晶体光纤设计及制备提供了理论指导. 光在空气孔中高强度、长距离传输, 为光与物质相互作用及非线性光纤光学提供了新的条件.
Photonic crystal fibers with an air hole in the core are analyzed by finite-element method. The relations of mode field distribution, confinement loss and dispersion characteristics with fiber structure parameter and wavelength are achieved. The principle of guiding light in air hole is explained by diffraction and the characteristics of photonic crystal fiber. For the fiber with low loss, single-mode, tightly confined light in the air core, the ranges of structure parameters and wavelengths are obtained. An optimal fiber structure is designed, of which the mode is tightly confined in the air core, and the confinement loss α=5.9× 10-5 dB/km. These provide theoretical instruction for the design and fabrication of photonic crystal fiber with an air hole in the core. The high intensity in an air hole, coupled with long interaction length, promises a new class of experiments in light-matter interaction and nonlinear fiber optics.