International audienceWe present an original design of anisotropic metamaterial plates exhibiting extraordinary transmission through perfectly conductor metallic screens perforated by a subwavelength double-pattern rectangular aperture array. The polarization properties of the fundamental guided mode inside the apertures are at the origin of the anisotropy. The metal thickness is a key parameter that is adjusted in order to get the desired value of the phase difference between the two transversal electromagnetic field components. As an example, we treat the case of a half-wave plate having 92% transmission coefficient. Such a study can be easily extended to design anisotropic plates operating in terahertz or microwave domains
We propose the design of a three-dimensional anisotropic chiral structure composed of double-layered metallic films. Each layer behaves as a half-wave plate thanks to the excitation and the propagation of guided modes inside the subwavelength apertures of each metallic layer. As in conventional optics, the optical rotation is tuned by simply changing the angle between the two plates. We numerically demonstrate that this property remains valid only if the whole second layer is rotated instead of twisting every pattern. Therefore, the plane of polarization can be rotated by any desired value and is accompanied by a transmission up to 80%. The proposed structure opens the way to the design of a new kind of chiral plate in the terahertz or microwave domains.
In this article, an extension of the spatial filter method to study Fabry‐Perot antennas with homogeneous or inhomogeneous partially reflecting surface (PRS) of finite size is proposed. This tool was subsequently validated through the study of different Fabry‐Perot antennas, with homogeneous PRS and inhomogeneous GRadient‐INdex (GRIN) PRS that present very high side lobe level (SLL). Since they are due to structure truncation, a new inhomogeneous PRS to reduce the SLL is designed with the new analytical tool. The new inhomogeneous PRS for Fabry‐Perot antenna is characterized by simulations and measurements. Compared to the homogeneous PRS antenna, the proposed PRS allows a SLL reduction of 5 dB without decreasing the 14 dBi directivity.
In this paper an approach based on the calculation of longitudinal and transverse operators is presented. The paper is devoted to the interesting topic of electromagnetic-wave propagation in complex (chiral) media. The studied process allows the analysis of guidedstructures with chiral-medium components. In this case the equations are continuously coupled. Using the longitudinal equations, we analyze wave propagation in a parallel-plate chirowaveguide consisting of two parallel perfectly conducting planes filled with a lossless, homogeneous, isotropic chiral material. The main feature of the guides is that the propagation modes are always hybrid. In addition, bifurcated modes exist with the same cutoff-frequency values and unequal propagation characteristics. We address here the issue of wave propagation in a rectangular chirowaveguide, by means of longitudinal and transverse operators. This topic was first addressed by Engheta and Pelet. (IEEE Trans. Antenna Propag. 38, 90 (1990)). We rederive their results, using a method based on a new mathematical approach that seems to be original.PACS Nos.: 41.20.Jb
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