新型矩形点阵光子晶体光纤的高双折射负色散效应

设计了一种新型矩形点阵光子晶体光纤,该光纤纤芯缺失一根空气柱,包层沿光纤长度方向在普通矩形点阵光子晶体光纤中每两列之间隔一行插入一列空气孔而形成正方形网孔结构.采用全矢量有限元法并结合各向异性完美匹配边界条件,对该光纤的色散、双折射和约束损耗进行了数值模拟.结果发现,该光纤具有高双折射负色散效应和较强的模约束能力,约束损耗小于10-2dB·m-1,通过改变光纤结构参数(即空气孔间隔Λ和相对孔间隔d/Λ),可以调节该光纤高双折射负色散工作波长.若调整光纤结构参数Λ=2.0μm,d/Λ=0.4,该光纤在C波段(1.53—1.565μm)呈现负色散并具有负色散斜率,双折射高达10-2,非线性系数接近55km-1W-1.该光纤将在保偏光通信、色散补偿以及基于四波混频的波长转换器设计等方面具有重要的应用.

High-birefringence negative dispersion effect of novel rectangular lattice photonic crystal fiber

A novel rectangular lattice photonic crystal fiber is proposed which is composed of a central defect core and a cladding with square mesh structure by introducing another air hole row between two air hole rows for every other line into a conventional rectangular lattice photonic crystal fiber. Its dispersion, birefringence and confinement loss are numerically investigated by full vector finite element method with anisotropic perfectly matched layers. Numerical results indicate that the proposed fiber shows higher birefringence negative dispersion effect and stronger confinement ability of guided mode, in which the confinement loss is lower than 10^-2 dB ·m^-1. The wavelength for high birefringence negative dispersion can be optimized by adjusting the parameters of proposed fiber, such as Λ and d/Λ. The dispersion and the dispersion slope are both negative, the birefringence is higher than 10^-2, and nonlinear parameter is close to 55 km^-1W^-1 over C band (i.e. 1.53—1.565 μm) under the condition of Λ=2.0 μm and d/Λ=0.4. This fiber will have important applications in the fields of polarization maintaining transmission system and dispersion compensation, and also in the design of widely tunable wavelength converter based on four-wave mixing.