Acoustic far-field focusing effect for two-dimensional graded negative refractive-index sonic crystals

Peng, Shasha; He, Zhaojian; Han, Je-Chin; Zhang, Anqi; Qiu, Chunyin; Ke, Manzhu; Liu, Zhengyou

doi:10.1063/1.3457447

Cited by 107 publications

(61 citation statements)

References 21 publications

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“…10 Like their optical counterparts, the proposed 2D GRIN SC lenses have flat surfaces and are of easier fabrication than curved SC lenses. More recently, a GRIN SC lens based on a different approach has been proposed and experimentally demonstrated; 11 it is designed for a frequency within the first acoustic band with negative slope. The drawback of this type of GRIN lenses, whose wavelengths are of the order of the lattice parameter, is that they work for the single operational frequency at which they have been designed.…”

mentioning

confidence: 99%

Sound focusing by gradient index sonic lenses

Climente

Torrent

Sánchez‐Dehesa

2010

Applied Physics Letters

190

141

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Gradient index sonic lenses based on two-dimensional sonic crystals are here designed, fabricated, and characterized. The index-gradient is achieved in these type of flat lenses by a gradual modification of the sonic crystal filling fraction along the direction perpendicular to the lens axis. The focusing performance is well described by an analytical model based on ray theory as well as by numerical simulations based on the multiple-scattering theory.

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mentioning

confidence: 99%

Sound focusing by gradient index sonic lenses

Climente

Torrent

Sánchez‐Dehesa

2010

Applied Physics Letters

190

141

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“…GRIN geometries are utilized for a broad range of metamaterial applications including scattering reduction [6,7], wave focusing [8][9][10][11][12][13][14][15][16], and bending [1][2][3]17,18]. In contrast to previous lens designs, we present a lens composed of impedance-matched, hollow-shell elements with sound speeds higher than water.…”

Section: Introductionmentioning

confidence: 94%

Transparent Gradient-Index Lens for Underwater Sound Based on Phase Advance

et al. 2015

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Spatial gradients in a refractive index are used extensively in acoustic metamaterial applications to control wave propagation through phase delay. This study reports the design and experimental realization of an acoustic gradient-index lens using a sonic crystal lattice that is impedance matched to water over a broad bandwidth. In contrast to previous designs, the underlying lattice features refractive indices that are lower than the water background, which facilitates propagation control based on a phase advance as opposed to a delay. The index gradient is achieved by varying the filling fraction of hollow, air-filled aluminum tubes that individually exhibit a higher sound speed than water and matched impedance. Acoustic focusing is observed over a broad bandwidth of frequencies in the homogenization limit of the lattice, with intensity magnifications in excess of 7 dB. An anisotropic lattice design facilitates a flatfaceted geometry with low backscattering at 18 dB below the incident sound-pressure level. A threedimensional Rayleigh-Sommerfeld integration that accounts for the anisotropic refraction is used to accurately predict the experimentally measured focal patterns.

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“…The versatility of devices that control acoustic wave propagation in a PC structure is further enhanced by introducing the concept of a gradient-index (GRIN). [13][14][15][16][17] GRIN PCs guide acoustic waves to follow a sinusoidal trajectory in the structure and thus can efficiently focus planar acoustic waves to a sub-wavelength spot or vise versa. Additionally, the wavelength-scale acoustic mirage effect in GRIN PCs can prove useful in the design of micro/ nanoscale acoustic circuits.…”

Section: Introductionmentioning

confidence: 99%

Design of acoustic beam aperture modifier using gradient-index phononic crystals

Lin

Tittmann

Huang

2012

Journal of Applied Physics

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This article reports the design concept of a novel acoustic beam aperture modifier using butt-jointed gradient-index phononic crystals (GRIN PCs) consisting of steel cylinders embedded in a homogeneous epoxy background. By gradually tuning the period of a GRIN PC, the propagating direction of acoustic waves can be continuously bent to follow a sinusoidal trajectory in the structure. The aperture of an acoustic beam can therefore be shrunk or expanded through change of the gradient refractive index profiles of the butt-jointed GRIN PCs. Our computational results elucidate the effectiveness of the proposed acoustic beam aperture modifier. Such an acoustic device can be fabricated through a simple process and will be valuable in applications, such as biomedical imaging and surgery, nondestructive evaluation, communication, and acoustic absorbers.

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Acoustic far-field focusing effect for two-dimensional graded negative refractive-index sonic crystals

Cited by 107 publications

References 21 publications

Sound focusing by gradient index sonic lenses

Sound focusing by gradient index sonic lenses

Transparent Gradient-Index Lens for Underwater Sound Based on Phase Advance

Design of acoustic beam aperture modifier using gradient-index phononic crystals

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