Abstract
This paper studies wave propagation in a periodic parallel-plate waveguide with equilateral triangular holes. A mode-matching method is implemented to analyze the dispersion diagram of the structure possessing glide and mirror symmetries. Both structures present an unexpected high degree of isotropy, despite the triangle not being symmetric with respect to rotations of 90°. We give some physical insight on the matter by carrying out a modal decomposition of the total field on the hole and identifying the most significant modes. Additionally, we demonstrate that the electrical size of the triangular hole plays a fundamental role in the physical mechanism that causes that isotropic behavior. Finally, we characterize the influence of the different geometrical parameters that conform the unit cell (period, triangle size, hole depth, separation between metallic plates). The glide-symmetric configuration offers higher equivalent refractive indexes and widens the stopband compared to the mirror-symmetric configuration. We show that the stopband is wider as the triangle size is bigger, unlike holey structures composed of circular and elliptical holes where an optimal hole size exists.
Highlights
Holey metasurfaces are obtained by etching small holes on a metallic plate in a periodic or locally periodic arrangement [1]
We characterize the influence of the different geometrical parameters that conform the unit cell on the wave propagation through the structure
We study the capabilities of triangular holes as electromagnetic bandgap (EBG ) structures
Summary
Holey metasurfaces are obtained by etching small holes on a metallic plate in a periodic or locally periodic arrangement [1]. A single metallic sheet etched with holes can support plasmon-like waves (the so-called spoof-plasmons) even in the absence of dielectric or losses [2], in close similarity to the propagation in corrugated surfaces [3,4]. In the former, the metasurfaces are mirrored one into the other one while, in the latter, they are off-shifted by half a period along the periodicity directions (see Figure 1) In this last configuration, modes propagating between the surfaces are low-dispersive over a large frequency band [7,8]. Modes propagating between the surfaces are low-dispersive over a large frequency band [7,8] Their stopbands benefit of stronger field attenuation and of a larger bandwidth with respect to the mirror-symmetric configuration [9,10].
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