Lai Chih-Hsien, Chang Hung-chun
Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan.
Opt Express. 2011 Jan 17;19(2):562-9. doi: 10.1364/OE.19.000562.
The reflection coefficient is one important parameter of the perfectly matched layer (PML). Here we investigate its effect on the modal analysis of leaky waveguide modes by examining three different leaky waveguide structures, i.e., the holey fiber, the air-core terahertz pipe waveguide, and the gain-guided and index-antiguided slab waveguide. Numerical results reveal that the typical values 10(-8) ~10(-12) are inadequate for obtaining the imaginary part of the complex propagation constant, and the suggested reflection coefficient would be much smaller, for example, 10(-50) or 10(-100). With such a small coefficient, both the computational window size and the PML thickness can be significantly reduced without loss of stability. Moreover, in some cases, the modal field profiles can only be accurately obtained with such a small coefficient.
反射系数是完全匹配层（PML）的一个重要参数。在此，我们通过研究三种不同的泄漏波导结构，即多孔光纤、空芯太赫兹管波导以及增益引导和折射率反引导平板波导，来考察其对泄漏波导模式模态分析的影响。数值结果表明，典型值10^(-8) ~ 10^(-12)不足以获得复传播常数的虚部，建议的反射系数要小得多，例如10^(-50)或10^(-100)。有了如此小的系数，计算窗口尺寸和PML厚度都可以显著减小而不损失稳定性。此外，在某些情况下，只有使用如此小的系数才能准确获得模态场分布。
