Xu Jing, Wu Bingbing, Chen Yuntian
Opt Express. 2015 May 4;23(9):11566-75. doi: 10.1364/OE.23.011566.
Mode properties of circularly symmetric waveguides with one special type of bianisotropy are studied using finite element approach. We find that the polarization degeneracy in circularly symmetric waveguides can be eliminated, by introducing intrinsic crossing coupling between electric and magnetic moments in the constituent units of the waveguide media. Breaking the polarization degeneracy in high order mode groups is also confirmed numerically. With the bianisotropic parameters chosen in this work, the x and y-polarized modes remain decoupled. Typically, the y-polarized modes remain completely unchanged, while the x-polarized modes are turned into leaky modes that are lossy along propagation direction. A perturbation model from coupled mode theory is developed to explain the results and shows excellent agreement. Such asymmetric behavior between different polarizations might be feasible and useful for developing compact polarizers in terahertz or mid-infrared regime.
采用有限元方法研究了具有一种特殊类型双各向异性的圆对称波导的模式特性。我们发现，通过在波导介质的组成单元中引入电矩和磁矩之间的固有交叉耦合，可以消除圆对称波导中的极化简并。数值计算也证实了高阶模组中极化简并的打破。在本工作中选择双各向异性参数后，x极化模式和y极化模式保持解耦。通常，y极化模式保持完全不变，而x极化模式转变为沿传播方向有损耗的泄漏模式。从耦合模理论发展了一个微扰模型来解释结果，并且显示出极好的一致性。不同极化之间的这种不对称行为对于在太赫兹或中红外波段开发紧凑型偏振器可能是可行且有用的。
