List of topics investigated in this chapter
Surface modes propagating along a single-interface structure composed of combinations of lossless, nondispersive DPS-, ENG-, DNG- and MNG-type media have been explored in the previous chapter. In this chapter we expand the investigation to double-interface structures and treat the properties depicted in Table 5.1. Here, however, the structures are restricted to those whose cover and substrate are composed of the same lossles DPS-type medium, and to guides composed of lossless DPS-, ENG-, DNG- and MNG-type media with real-valued ϵr and μr. The propagation constant, β, is calculated for a freely propagating mode, and the electric (E) and magnetic (H) fields are evaluated together with the local power flow, sz. The mode solutions were adapted from Refs.  and .
Geometry of the system
Figure 5.1 is a schematic diagram of a double-interface structure composed of a substrate, a guide with thickness dg and a cover. We assume the existence of a surface mode at this double-interface structure whose propagation constant, β, points along the z-direction, and the normal to the interface is along the x-direction. The thickness of the guide adds another parameter when solving for the modes that this structure can support. In particular, for a symmetric structure where the guide is a DNG-type, there is a critical guide thickness, dcr, below which the modes exhibit unique properties.