Acoustic flat lensing using an indefinite medium

Acoustic flat lensing is achieved here by tuning a phononic array to have indefinite medium behaviour in a narrow frequency spectral region along the acoustic branch. This is confirmed by the occurrence of a flat band along an unusual path in the Brillouin zone and by interpreting the intersection p...

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Bibliographic Details
Published in:arXiv.org 2018-10
Main Authors: Dubois, M, Perchoux, J, Vanel, A L, Tronche, C, Achaoui, Y, Dupont, G, Bertling, K, Rakic, A D, Antonakakis, T, Enoch, S, Abdeddaim, R, Craster, R V, Guenneau, S
Format: Article
Language:English
Subjects:
Acoustics
Beams (radiation)
Brillouin zones
Optical feedback
Online Access:Get full text
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Summary:Acoustic flat lensing is achieved here by tuning a phononic array to have indefinite medium behaviour in a narrow frequency spectral region along the acoustic branch. This is confirmed by the occurrence of a flat band along an unusual path in the Brillouin zone and by interpreting the intersection point of isofrequency contours on the corresponding isofrequency surface; coherent directive beams are formed whose reflection from the array surfaces create lensing. Theoretical predictions are corroborated by time-domain experiments, airborne acoustic waves generated by a source with a frequency centered about \(10.6\) kHz, placed at three different distances from one side of a finite phononic crystal slab, constructed from polymeric spheres, yield distinctive focal spots on the other side. These experiments evaluate the pressure field using optical feedback interferometry and demonstrate precise control of the three-dimensional wave trajectory through a sonic crystal.
ISSN:2331-8422