Abstract
The recently proposed concept of metamaterials has opened exciting venues to control wave-matter interactions in unprecedented ways. Here, we demonstrate the relevance of metamaterials for inducing acoustic birefringence, a phenomenon which has already found its versatile applications in optics in designing light modulators or filters, and nonlinear optic components. This is achieved in a suitably designed acoustic metamaterial which is non-Eulerian, in the sense that at low frequencies, it cannot be homogenized to a uniform acoustic medium whose behavior is characterized by the Euler equation. Thanks to the feasibility of engineering its subwavelength structure, such a non-Eulerian metamaterial allows one to desirably manipulate the birefringence process. Our findings may give rise to the generation of novel devices such as tunable acoustic splitters and filters.
Highlights
Isotropic homogeneous electromagnetic (Maxwellian) media support only one propagating mode in the quasistatic limit,[1,2] where the ratio between spatial and temporal scales is much smaller than the velocity at which the mode propagates.[3,4] Some anisotropic media, behave differently in the sense that they can support more than one mode at a given low frequency with distinct characteristics.[5,6,7] each of these modes corresponds to a unique dispersion relation depending on the material orientation
We demonstrate the relevance of metamaterials for inducing acoustic birefringence, a phenomenon which has already found its versatile applications in optics in designing light modulators or filters, and nonlinear optic components
We have demonstrated the birefringence phenomenon for sound waves
Summary
Isotropic homogeneous electromagnetic (Maxwellian) media support only one propagating mode in the quasistatic limit,[1,2] where the ratio between spatial and temporal scales is much smaller than the velocity at which the mode propagates.[3,4] Some anisotropic media, behave differently in the sense that they can support more than one mode at a given low frequency with distinct characteristics.[5,6,7] each of these modes corresponds to a unique dispersion relation depending on the material orientation. The recently developed field of metamaterials,[23–58] has offered the intriguing possibility of realizing artificial structures that, once engineered, can exhibit desired bulk properties Such composites have allowed realization of materials with exotic features such as negative refractive index, offering platforms for various unconventional wave phenomena such as wave cloaking,[59] focusing,[60] imaging,[61] and wavefront modulation.[62]. They have enabled the synthesis of electromagnetic artificial composites supporting two or even an arbitrarily large number of low-frequency modes.[63]. Our proposed birefringent metamaterial allows one to control the directions and the number of refracted beams, by tailoring its subwavelength structure
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