Loss-induced Enhanced Transmission in Anisotropic Density-near-zero Acoustic Metamaterials

Abstract

Anisotropic density-near-zero (ADNZ) acoustic metamaterials are investigated theoretically and numerically in this paper and are shown to exhibit extraordinary transmission enhancement when material loss is induced. The enhanced transmission is due to the enhanced propagating and evanescent wave modes inside the ADNZ medium thanks to the interplay of near-zero density, material loss, and high wave impedance matching in the propagation direction. The equi-frequency contour (EFC) is used to reveal whether the propagating wave mode is allowed in ADNZ metamaterials. Numerical simulations based on plate-type acoustic metamaterials with different material losses were performed to demonstrate collimation and subwavelength imaging enabled by the induced loss in ADNZ media. This work provides a different way for manipulating acoustic waves.

Plasmon canalization and tunneling over anisotropic metasurfaces

“…phenomenon of energy collimation and omnidirectional enhancement of transmission between dissimilar media, even for grazing incidence [6], [7]. These findings have triggered the pursuit of practical implementations of this phenomenon not only at radiofrequencies and optical frequencies but also in acoustics [8], [9]. Current electromagnetic realizations rely on 3D metamaterials, that not only suffer from well-known issues like challenging fabrication and large volumetric loss [1], [10], [11], but also present no advantage over thin films in terms of near-field interactions with external sources [12].…”

Artificial double-zero-index materials

“…Looking into the future, we believe DZIM will continue to advance the field. Considering complex parameters and anisotropy in DZIM offers new possibilities to control waves [68][69][70][71]. For example, the double-zero-index property boosts the effect of non-Hermitian perturbations, thus small loss can lead to large absorption.…”

“…For example, the double-zero-index property boosts the effect of non-Hermitian perturbations, thus small loss can lead to large absorption. Some people combine the concept of BIC with ZIM to realize low-loss DZIM, while others utilize loss in ZIM to realize interesting phenomena such as collimation, enhancement of transmission, and coherent perfect absorption [68][69][70]. Recently, zero-index was introduced to a bianisotropic material, extending the concept of ZIM to topology [71].…”

Anisotropic index-near-zero metamaterials for enhanced directional acoustic emission

“…In order to get more accurate effective parameters, we modify the original parameter retrieval method via introducing an undetermined imaginary term in previously obtained ρ x . This term has an evident effect on the propagation property of the waves, especially in terms of transmission [37][38][39], and can be obtained by inverse design [40,41], which has been used for the design optimization of metamaterial for a wide range of applications and is very suitable for the current case.…”