基于全矢量模式匹配法的三维弯曲波导本征模式计算

采用精确、严格的全矢量模式匹配法，计算了三维脊型弯曲波导和条形弯曲波导的本征模式，分析了模式折射率和辐射损耗随弯曲半径的变化关系.计算结果与已报道的有限差分法的结果符合很好.对文献中已报道但没有深入分析的现象给出了合理的解释.半径为50和12 μm的条形波导的计算结果表明：当波导的弯曲半径减小时，发生在分界面处的TE-TM模耦合会显著增强，这将导致弯曲波导中的模式不再是传统意义上的准TE模和准TM模，而是混合模.随着半径的减小，混合模的横向分量之间的差异会减小，当两个横向分量达到近似相等的强度时，波导的偏振相关性将会大大减小. 关键词： 导波光学 全矢量模式匹配法 微环谐振腔 光波导理论

Application of full vectorial mode matching method to the calculation of eigenmodes of three-dimensional bent waveguide

The eigenmodes of bent rib and bent strip waveguides are calculated by accurate and rigorous full vectorial mode matching method. Mode index and bending loss are presented as functions of bending radius. The computation result shows an excellent agreement with that obtained by finite difference method. Comparison of the strip waveguides with radius of 12 and 50 μm indicates that the phenomena of TE-TM coupling occurring on the side wall will become very strong when the bending radius is decreased, and this is the reason why the modes in the bend waveguide with small radius are hybrid mode instead of TE mode or TM mode in the traditional sense. The difference between transverse components of hybrid mode will be abated if the bending loss decreased, and when the two components are comparable, the polarization dependence of bent waveguide will decrease greatly.