Wave Propagation in Periodic Metallic Structures with Equilateral Triangular Holes
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AuthorAlex-Amor, Antonio; Valerio, Guido; Ghasemifard, Fatemeh; Mesa Aguado, Francisco Luis; Padilla De La Torre, Pablo; Fernández-González, José M.; Quevedo Teruel, Óscar
Periodic structuresEquilateral triangular holesMode-matchingDispersion analysisGlide symmetryMirror symmetry
Alex-Amor, A., Valerio, G., Ghasemifard, F., Mesa, F., Padilla, P., Fernández-González, J. M., & Quevedo-Teruel, O. (2020). Wave Propagation in Periodic Metallic Structures with Equilateral Triangular Holes. Applied Sciences, 10(5), 1600.
SponsorshipThis work was partially funded by the Spanish Ministerio de Ciencia Innovación y Universidades under the project TIN2016-75097-P, and with European Union FEDER funds under projects TEC2017-84724-P and TEC2017-85529-C3-1-R, by the French National Research Agency Grant Number ANR-16-CE24-0030, by the Vinnova project High-5 (2018-01522) under the Strategic Programme on Smart Electronic Systems, and by the Stiftelsen Åforsk project H-Materials (18-302).
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 90º. 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.