Homogenization of Thin and Thick Metamaterials and Applications

The wave propagation in structures involving metamaterials can be described owing to homogenization approaches which allow to replace the material structured at the subwavelength scale by an equivalent and simpler, effective medium. In its simplest form, homogenization predicts that the equivalent medium is homogeneous and anisotropic and it is associated to the usual relations of continuity for the electric and magnetic fields at the boundaries of the metamaterial structure. However, such prediction has a range of validity which remains limited to relatively thick devices and it is not adapted to more involved geometries (notably three-dimensional). The following two aspects are considered: (i) we study how the homogenization at the leading order can be improved when the thickness of the device becomes small and (ii) we propose a heuristic extension of the solution given by the leading order homogenization in order to deal with a complex geometry; in the latter case, an application to a demultiplexer device is proposed

Peco et l’Euro.

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Backscattering reduction in a twisted water wave channel

We study theoretically and experimentally how to reduce the backscattering of water waves in a channel with multiple turns. We show that it is not only possible to cancel backscattering but also to achieve a remarkable transmission in such geometries. In order to avoid the reflection that naturally arises at each turn of the waveguide, an anisotropic metamaterial made of closely-spaced thin vertical plates is used. The efficiency of the metamaterial arrangement depends only slightly on the frequency of the incident wave, as long as its wavelength is much larger than the periodicity of the array. This phenomenon is not restricted only to water wave channels but also applies to any type of waves with Neumann boundary conditions

Diffraction grating with space-time modulation

International audienc