含左手材料四层平板波导的模式特性

Mode Characteristics in a Four-layer Slab Waveguide with the Left-handed Material

关键词:  平板波导  左手材料  转移矩阵法  模式本征方程

Key words:  slab waveguide  left-handed material  transfer matrix method  mode equation

摘要:

[目的]研究一个中间两层为左手材料,覆盖层和衬底层为右手材料的四层平板波导(RHM-LHM-LHM-RHM)系统。[方法]用数值计算波导的色散曲线,画出不同模式的电场分布图。[结果]该波导存在TE₀模和TM₀模,高阶模式的TE模和TM模会出现双模现象,在特定的波导层厚度下,TE_m模和TM_m模的有效折射率相同。缓冲层的厚度和介电常数越大,TM模的双模现象越显著。模系数m为奇数或偶数的电场分布图相似,但波导层厚度越大,其电场振荡越强,而缓冲层的电场振荡基本不变。[结论]通过控制左手材料的介质参数可以灵活改变波导的模式特性。

Abstract:

[Objective] The guided modes are studied in a four-layer left-handed material slab waveguide structure with two negative refractive materials inside and surrounded by two normal dielectrics.[Methods] Universal dispersion curves are calculated numerically, and the transverse profile of TE mode and TM mode with different mode number are obtained.[Results] The fundamental mode is exist in the proposed structure, mode-double-degeneracy appears for the high-order modes of TE mode and TM mode, and in the specific thickness of guided layer, the TE mode and TM mode in the same order have identical effective index.With the increase of buffer layer's thickness and permittivity, the mode-double-degeneracy of TM mode is more obvious.The transverse profiles are similar when the mode number m is odd or even. However, as the thickness of guided layer increases, the oscillating transverse profile is stronger in the waveguide, but is almost unchanged in the buffer layer.[Conclusion] The mode characteristics of waveguide can be flexibly converted by controlling dielectric parameters of LHM.