Elliptic pillars based metasurface for elastic waves focusing in a plate
L. Carpentier,
A. Gueddida,
G. Lévêque,
R. Alcorta-Galvan,
C. Croënne,
M. Miniaci,
B. Djafari-Rouhani,
Y. Pennec
Affiliations
L. Carpentier
Institut d’Electronique, de Microélectronique et de Nanotechnologies, UMR CNRS 8520, Université de Lille, 59650 Villeneuve d’Ascq, France
A. Gueddida
Institut d’Electronique, de Microélectronique et de Nanotechnologies, UMR CNRS 8520, Université de Lille, 59650 Villeneuve d’Ascq, France
G. Lévêque
Institut d’Electronique, de Microélectronique et de Nanotechnologies, UMR CNRS 8520, Université de Lille, 59650 Villeneuve d’Ascq, France
R. Alcorta-Galvan
Univ. Lille, CNRS, Centrale Lille, Junia, University Polytechnique Hauts-de-France, UMR 8520 - IEMN - Institut d’Electronique de Microélectronique et de Nanotechnologie, F-59000 Lille, France
C. Croënne
Univ. Lille, CNRS, Centrale Lille, Junia, University Polytechnique Hauts-de-France, UMR 8520 - IEMN - Institut d’Electronique de Microélectronique et de Nanotechnologie, F-59000 Lille, France
M. Miniaci
Univ. Lille, CNRS, Centrale Lille, Junia, University Polytechnique Hauts-de-France, UMR 8520 - IEMN - Institut d’Electronique de Microélectronique et de Nanotechnologie, F-59000 Lille, France
B. Djafari-Rouhani
Institut d’Electronique, de Microélectronique et de Nanotechnologies, UMR CNRS 8520, Université de Lille, 59650 Villeneuve d’Ascq, France
Y. Pennec
Institut d’Electronique, de Microélectronique et de Nanotechnologies, UMR CNRS 8520, Université de Lille, 59650 Villeneuve d’Ascq, France
In this paper, the ability of a metasurface made of resonant elliptical pillars to focus flexural Lamb waves in the sub-wavelength regime is investigated. We report on the influence of the ellipticity parameter on the local resonances of the pillars, in particular the monopolar compressional and dipolar bending modes that are responsible for the desired focusing effect. We also discuss how the transmission through a line of pillars reveals these modes when the orientation of the pillars is changed with respect to the incident wave. Both the resonances can be superimposed for a particular choice of the ellipticity parameter, allowing a phase shift of 2π in the transmission coefficient for an incident antisymmetric Lamb wave, which is a necessary condition for the design of the metasurface. Finally, a gradient design for the pillar ellipticity is investigated, and its capacity to choose the focusing directionality of the transmitted wave at different targeted points is demonstrated.
