Surface and Leaky Modes in a Symmetric DPS-DNG Slab

Abstract

Recent experimental verification of metamaterials with negative index of refraction – also known as DNG (double negative) media as their permittivity and permeability are both negative – has led to the widespread research of guiding structures that are made of (or include) these new metamaterials. The unusual properties exhibited by DNG materials, such as backward wave propagation and antiparallel phase and group velocities, makes them suitable for new microwave devices. One such device is the DNG open waveguide studied by Shadrivov et al. (I. V. Shadrivov, A. A. Sukhorukov, and Y. S. Kivshar, Phys. Rev. E, 67, 057602, 2003) where the propagation properties of guided modes were analyzed. We present a variation of this waveguide and study not only guided modes but also leaky modes. The study of leaky modes in open dielectric waveguides was analyzed by Tamir and Oliner back in 1963 (T. Tamir, A. Oliner, Proc. IEE, 110, 310-334, 1963). In this paper a symmetrical DPS-DNG structure, as shown in the inset of Figure 1, is analyzed. The modal equation is obtained for TE and TM modes. However, surface as well as leaky modes were investigated when numerically solving the modal equation. Figure 1 shows the dispersion curve of the fundamental TE mode, where v is a normalized frequency. In the presentation, the dispersion diagrams for both surface and leaky modes will be discussed. The appearance of stop-bands in guided modes and the occurrence of leaky modes (for 1 eff n > ) are addressed – two effects that do not exist in conventional or DPS (double positive) waveguides. Finally, a comparison between this structure and a conventional DPS-DPS waveguide is given in order to highlight the new specific characteristics that are induced by the DNG material.