Three-dimensional acoustic lenses with axial symmetry

Sánchis, Lorenzo; Yáñez, Andrés Suárez; Galindo, Pedro L.; Pizarro, J.; Pastor, Juan Martínez

doi:10.1063/1.3474616

Cited by 25 publications

(21 citation statements)

References 16 publications

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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%

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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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Section: Introductionmentioning

confidence: 94%

“…We emphasize that the 2D lattice focuses only along one axis (y axis), resulting in lower magnifications than would be produced by axisymmetric 3D designs [26,27]. The magnification can be increased by extending our 2D design to three dimensions using tubes bent into a toroid configuration [12,15].…”

Section: The Upper Panels [(A)-(c)] Inmentioning

confidence: 99%

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

et al. 2015

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“…On the other hand, in the diffractive regime, in Ref. 22 the authors propose to maximize the focusing properties in a 2D system of cylindrical rigid scatterers embedded in air and obtain, by rotation of the optimized structure, an axial symmetric lens formed by rigid toroidal scatterers. The structure was validated experimentally and the obtained sound amplification in the focus was remarkably high, showing that the rotational symmetry of the system increases its efficiency.…”

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confidence: 99%

“…The axisymmetric lenses however present a symmetry matching with radial symmetric sources as, for example, the circular radiating piston. The asymptotic limits of this circular radiating piston are the infinite radiating plane (radiating an unbounded plane wave) and the point sources.Some recent works introduce axisymmetric discrete systems 21,22 with the aim of focalizing optical or acoustical waves. In the refractive regime, a transformational design of an axial symmetric three-dimensional GRIN lens was theoretically proposed in Ref.…”

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confidence: 99%

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Wave focusing using symmetry matching in axisymmetric acoustic gradient index lenses

Romero‐García

Cebrecos

Picó

et al. 2013

Applied Physics Letters

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The symmetry matching between the source and the lens results of fundamental interest for lensing applications. In this work we have modeled an axisymmetric gradient index (GRIN) lens made of rigid toroidal scatterers embedded in air considering this symmetry matching with radially symmetric sources. The sound amplification obtained in the focal spot of the reported lens (8.24 dB experimentally) shows the efficiency of the axisymmetric lenses with respect to the previous Cartesian acoustic GRIN lenses. The axisymmetric design opens new possibilities in lensing applications in different branches of science and technology.PACS numbers: 43.20.Fn, 43.20.Gp, 43.20.Mv, Photonic 1,2 and phononic 3,4 crystals have been revealed in the last years as promising alternatives to control the propagation of electromagnetic and acoustic waves respectively and, based on new physical concepts, with extensive applications in both optics 5 and acoustics 6 . Depending on the ratio between the wavelength of the incident wave, λ, and the lattice constant of the crystals, a, the basic mechanism describing the action of the crystal on the wave can be best interpreted in terms of refraction 7 or diffraction 9 . In the long wavelength regime, i.e., λ >> a, crystals can be considered as homogeneous materials with effective properties 10,11 , therefore one can design refractive 7 or gradient index (GRIN) 12 lenses to control waves. In this direction, metamaterial acoustic GRIN lenses have recently been designed by using unit cells based on cross-shape scatterers 13 and on coiling up space 14 , providing a high transmission efficiency and small size. On the other hand, the case λ a corresponds to diffractive regime, where the crystal is strongly dispersive. Yang et al. 15 reported the first three dimension (3D) phononic crystal showing the focusing of ultrasonic waves in this regime. Since then several phononic lenses have been designed by using the curvature properties of the isofrequency contours, making use of the all angle negative refraction 16 and the convex isofrequency contours 17 .In most of the practical situations the sound wave sources have radial symmetry. Examples can be found in domains as aeroacoustics, microfluidics or medical ultrasound. In this situation the symmetry of the lens becomes relevant and one should consider the full source- lens system in order to improve the efficiency of the joint focusing device. Most of the focusing mechanisms described above have been conceived for cartesian lenses (those presenting translational symmetry, as for example a squared array of cylinders), which do not match with the radial symmetry of the source. A cartesian lens in general match with a semi-infinite rectangular radiating surface, which in the asymptotic limits, corresponds to a plane (radiating an unbounded plane wave) or to a line (radiating a cylindrical beam). The axisymmetric lenses however present a symmetry matching with radial symmetric sources as, for example, the circular radiating piston. The asymptotic limits of th...

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Planar Ultrasonic Lenses Formed by Concentric Circular Sandwiched‐Ring Arrays

Xia

Cai

et al. 2018

Adv Materials Technologies

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An underwater ultrasonic planar lens is numerically and experimentally developed with a small thickness and maintains a highly efficient transmission. The lens is formed by an array of concentric circular resin rings sandwiched between two identical silicone rings. Since the velocity of the water is closely in between that of the resin and silicone, a 2π phase variation can be achieved by changing the thickness ratios of the resin to the silicone ring within a thin sandwiched structure. Based on this principle, both single‐point and multipoint focusing lenses with high transmission in the axial direction are realized, which are believed to have potential applications in underwater imaging and detection.

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Three-dimensional acoustic lenses with axial symmetry

Cited by 25 publications

References 16 publications

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

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

Wave focusing using symmetry matching in axisymmetric acoustic gradient index lenses

Planar Ultrasonic Lenses Formed by Concentric Circular Sandwiched‐Ring Arrays

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