建立了基于透明边界条件(TBC)的全矢量迦辽金有限元法(FEM)分析二维光子晶体光纤(PCF)的模型,并对椭圆芯等5种高双折射光子晶体光纤基模的模式双折射、限制损耗及色散特性进行了数值分析和比较。通过减小内包层中沿x方向的空气孔,增大沿y方向的空气孔构成的一种光子晶体光纤的模式双折射在波长1550 nm处高达5.96×10-3,而椭圆芯光子晶体光纤为1.52×10-3。研究表明,可通过增加内包层中两个正交方向上空气孔的尺寸差来获得高双折射; 同时还得出内包层中放大的空气孔减小限制损耗,增加色散,而减小空气孔尺寸带来的影响则刚好相反; 内包层上空气孔数量越少,色散越平坦。

The model of full vector Galerkin finite element method (FEM) with transparent boundary conditions (TBC) is established. The modal birefringence, confinement loss and dispersion of the fundamental mode of five kinds highly birefringent photonic crystal fibers (PCFs) with elliptical cores are analyzed and compared. The modal birefringence of a photonic crystal fiber, which is formed by diminishing air holes along x-direction and enlarging air holes along y-direction in inner cladding, is 5.96×10-3 at the wavelength of 1550 nm, while that of a photonic crystal fiber with elliptical core is 1.52×10-3. The results show that high birefringence can be obtained by increasing the difference of air holes size along orthogonal direction in inner cladding. It is also proved that enlarged air holes of inner cladding reduce the confinement loss, and increase the dispersion, but the impact of diminished air holes is reversed; the fewer the air holes in inner cladding are, the flatter the dispersion is.