含单负材料对称三层平板波导的模式特性

由电磁场的波动方程和边界条件建立了单负材料作为芯层的对称三层平板波导的模式本征方程，用图解法研究其色散特性。研究发现，单负介质波导不支持快波的传播，只支持表面波的传播。在负磁材料平板波导中只存在TE表面模，不存在TM表面模。分析了在负磁材料平板波导中TE模受磁导率的比值-μ2／μ1和波导参数的影响，给出了横向场分布图。在-μ2/μ1〈1时，偶对称只有TE0表面模存在，奇对称只有TE1表面模存在，高阶模式并不存在，且两种模式都没有低频截止；-μ2/μ1〉1时，TE1表面模始终不出现；TE0模的存在与否和波导参数有关，在一定条件下TE0模可出现双模并存。给出的结果可望对表面波器件的设计提供理论基础。

Mode characteristics in a symmetrical three- slab waveguide with single- negative materials

According to Maxwell equations and boundary conditions of electromagnetic field, the mode eigen equations are obtained in a three - layer symmetrical slab waveguide with single - negative material. The graphic method is used to study their mode dispersion characteristics of even and odd symmetric modes which propagate along the waveguide with negative magnetic permeability material as core layer. The results prove that only TEl surface waves can propagate in this waveguide system. The TE surface modes are affected by the ratio of magnetic permeability - μ2/μ1 and the guide parameters. When - μ2/μ1 〈 1 ,only TE0 and TE1 surface waves do exist, and the higher - order TE modes do not exist at all. When -μ2/μ1 〉 1, the TE1 mode does not exist either. The two TE0 surface modes with different propagation constants in the same frequency can coexist under a certain condition. These results might give a theoretical basis for designing of surface wave devices.