Measurement of a Broadband Negative Index with Space-Coiling Acoustic Metamaterials

Abstract

We report the experimental demonstration of broadband negative refractive index obtained in a labyrinthine acoustic metamaterial structure. Two different approaches were employed to prove the metamaterial negative index nature: one-dimensional extractions of effective parameters from reflection and transmission measurements, and two-dimensional prism-based measurements that convincingly show the transmission angle corresponding to negative refraction. The transmission angles observed in the latter case also agree very well with the refractive index obtained in the one-dimensional measurements and numerical simulations. We expect this labyrinthine metamaterial to become the unit cell of choice for practical acoustic metamaterial devices that require broadband and significantly negative indexes of refraction.

Negative Refraction and Energy Funneling by Hyperbolic Materials: An Experimental Demonstration in Acoustics

“…Negative refraction was previously demonstrated using acoustic metamaterials based on space coiling [8,9], the drawbacks of these structures being their difficult fabrication in comparison with those studied here and their strong lossy characteristics [10]. Negative refraction was also demonstrated in phononic crystals with a fluid (liquid or air) matrix surrounding solid inclusions [11,12] and recently using a foamlike metallic structure [13].…”

Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface

“…A recently proposed category of acoustic metamaterials, termed labyrinthine metamaterials 14,21,22 , shows promise as building blocks for such wavefront-shaping metasurfaces. This family of unit cells features high energy throughput, broad complex (amplitude and phase) modulation range and non-resonant dispersion.…”

Design of double negativity elastic metamaterial

“…Although a number of double negativity (DN) acoustic metamaterials have been investigated [7][8][9][10][11][12][13][14][15], there are few reports in literature on DN elastic metamaterials. Among the elastic metamaterials that have been published, Wang theoretically investigated the mechanism of negative mass and/or negative modulus of lumped mass models [16].…”