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

García-Chocano, Victor M.; Christensen, Johan; Sánchez‐Dehesa, José

doi:10.1103/physrevlett.112.144301

Cited by 152 publications

(96 citation statements)

References 15 publications

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“…Subwavelength imaging has been demonstrated experimentally with PCs 12 and super-resolution of a PC flat lens has been achieved by resonantly amplifying evanescent waves 13 . More recently, Christensen et al 14,15 proposed a holey anisotropic metamaterial to obtain subwavelength NR and focusing by using the hyperbolic dispersion of a sound wave. The dependence of the band structure on periodically arranged unit cells usually limits the practical applications of PCs, often by requiring the size of the device to be the same order of magnitude as the acoustic wavelength.…”

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confidence: 99%

Negative refraction of elastic waves at the deep-subwavelength scale in a single-phase metamaterial

et al. 2014

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Negative refraction of elastic waves has been studied and experimentally demonstrated in three-and two-dimensional phononic crystals, but Bragg scattering is impractical for low-frequency wave control because of the need to scale the structures to manageable sizes. Here we present an elastic metamaterial with chiral microstructure made of a single-phase solid material that aims to achieve subwavelength negative refraction of elastic waves. Both negative effective mass density and modulus are observed owing to simultaneous translational and rotational resonances. We experimentally demonstrate negative refraction of the longitudinal elastic wave at the deep-subwavelength scale in the metamaterial fabricated in a stainless steel plate. The experimental measurements are in good agreement with numerical simulations. Moreover, wave mode conversion related with negative refraction is revealed and discussed. The proposed elastic metamaterial may thus be used as a flat lens for elastic wave focusing.

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Negative refraction of elastic waves at the deep-subwavelength scale in a single-phase metamaterial

et al. 2014

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“…Our metasurface is essentially a metamaterial/ phononic crystal hybrid structure 10 and both the local and non-local responses can be leveraged for the purpose of shaping the wavefront with a much larger degree of control than traditional acoustic wave manipulation methods. Such thin planar acoustic metasurfaces, along with existing bulk metamaterials [11][12][13][14][15][16][17][18][19][20] , provide a new design methodology for acoustic wave modulation, sensing and imaging applications.…”

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Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface

et al. 2014

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Metasurfaces are a family of novel wavefront-shaping devices with planar profile and subwavelength thickness. Acoustic metasurfaces with ultralow profile yet extraordinary wave manipulating properties would be highly desirable for improving the performance of many acoustic wave-based applications. However, designing acoustic metasurfaces with similar functionality to their electromagnetic counterparts remains challenging with traditional metamaterial design approaches. Here we present a design and realization of an acoustic metasurface based on tapered labyrinthine metamaterials. The demonstrated metasurface can not only steer an acoustic beam as expected from the generalized Snell's law, but also exhibits various unique properties such as conversion from propagating wave to surface mode, extraordinary beam-steering and apparent negative refraction through higher-order diffraction. Such designer acoustic metasurfaces provide a new design methodology for acoustic signal modulation devices and may be useful for applications such as acoustic imaging, beam steering, ultrasound lens design and acoustic surface wave-based applications.

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“…Acoustic metamaterials are a broad family of engineered materials which can be designed to possess flexible and unusual effective properties (12,13). In the past, acoustic metamaterials with high anisotropy (14,15), extreme nonlinearity (16), or negative dynamic parameters (density, bulk modulus, refractive index) (17)(18)(19)(20) have been realized. Applications such as scattering reducing sound cloak (21,22), beam steering metasurface (23), and other wave manipulating devices (24)(25)(26)(27) have been proposed and demonstrated.…”

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Single-sensor multispeaker listening with acoustic metamaterials

Xie

Tsai

Konneker

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Designing a "cocktail party listener" that functionally mimics the selective perception of a human auditory system has been pursued over the past decades. By exploiting acoustic metamaterials and compressive sensing, we present here a single-sensor listening device that separates simultaneous overlapping sounds from different sources. The device with a compact array of resonant metamaterials is demonstrated to distinguish three overlapping and independent sources with 96.67% correct audio recognition. Segregation of the audio signals is achieved using physical layer encoding without relying on source characteristics. This hardware approach to multichannel source separation can be applied to robust speech recognition and hearing aids and may be extended to other acoustic imaging and sensing applications. metamaterials | cocktail party problem | compressive sensing T he "cocktail party" or multispeaker listening problem is inspired by the remarkable ability of the human's auditory system in selectively attending to one speaker or audio signal in a multiple-speaker noisy environment (1, 2). Over the past half a century (3), the quest to understand the underlying mechanism (4-6) and build functionally similar devices has motivated significant research efforts (4-8).Previously proposed engineered multispeaker listening systems generally fall into two categories. The first kind is based on audio features and linguistic models of speech. For example, harmonic characteristics, temporal continuity, onset/offset of speech units combined with hidden Markov language models can be used to group overlapping audio signals into different sources (7, 9, 10). The drawback of such an approach is that certain audio characteristics have to be assumed (e.g., nonoverlapping in spectrogram) and linguistic model-based estimation can be very computationally intensive. The second kind relies on multisensor arrays to spatially filter sources (11). The need for multiple transducers and system complexity are the major disadvantages of the second approach.In this work, we demonstrate a multispeaker listening system that separates overlapping simultaneous conversations by leveraging the wave modulation capabilities of acoustic metamaterials. Acoustic metamaterials are a broad family of engineered materials which can be designed to possess flexible and unusual effective properties (12, 13). In the past, acoustic metamaterials with high anisotropy (14, 15), extreme nonlinearity (16), or negative dynamic parameters (density, bulk modulus, refractive index) (17-20) have been realized. Applications such as scattering reducing sound cloak (21, 22), beam steering metasurface (23), and other wave manipulating devices (24-27) have been proposed and demonstrated. We demonstrate here that acoustic metamaterials can also be useful for encoding independent acoustic signals coming from different spatial locations by creating highly frequency-dependent and spatially complex measurement modes (28), and aid the solution finding for the inverse problem. Such ph...

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

Cited by 152 publications

References 15 publications

Negative refraction of elastic waves at the deep-subwavelength scale in a single-phase metamaterial

Negative refraction of elastic waves at the deep-subwavelength scale in a single-phase metamaterial

Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface

Single-sensor multispeaker listening with acoustic metamaterials

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