Experimental and Theoretical Evidence for Subwavelength Imaging in Phononic Crystals

Sukhovich, Alexey; Merheb, B.; Muralidharan, Krishna; Vasseur, J. O.; Pennec, Yan; Deymier, Pierre A.; Page, John H.

doi:10.1103/physrevlett.102.154301

Cited by 280 publications

(175 citation statements)

References 26 publications

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“…Intense Bragg scattering at the Brillouin zone can also result in the extreme deformation of the second band EFCs in PCs, which leads to backward-wave NR 11 . 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.…”

mentioning

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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confidence: 99%

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

et al. 2014

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“…The successful application of transformation optics to wave modulation in cylindrical coordinates modulates the omnidirectional line radiation source to specified patterns and directions 13 . In addition to radiation pattern control, the modulation of the wave can also produce phenomena such as lensing and hyperlensing [14][15][16][17] .…”

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confidence: 99%

Effective impedance boundary optimization and its contribution to dipole radiation and radiation pattern control

Liu

et al. 2014

Nat Commun

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Radiation pattern control has generated much interest recently due to its potential applications. Here we report the observation of high-efficiency dipole-like radiation of sound with broad bandwidth through a decorated plate with periodical two-dimensional Helmholtz resonators on both sides and a single slit at the centre. The decorated plate was optimally designed to adjust the effective impedance of the boundary, and the underlying mechanism of radiation pattern control is attributed to wave vector tailoring. The high radiation efficiency is due to the Fabry-Perot resonances associated with waveguide modes in the centre slit. The method to obtain a collimated beam without any sidelobes is also provided. Our findings should have an impact on acoustic applications.

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“…Recently, efforts in this direction have been intensified [14,36,37,38], taking advantage of the progress achieved in nanofabrication. A reduction of the FWHM of the central spot below /2 at the expense of large sidebands has also been observed in Veselago-type acoustic focusing by phononic-crystal structures without apodization [15,33]. In either case, no contradiction to the proposed definitions of the diffraction limit arises.…”

Section: Super-resolution/superoscillationsmentioning

confidence: 81%

“…Despite the limitations of the superlens restricting its effect to the near field, the excitement generated by Pendry's paper led to extensive work on subwavelength focusing and imaging, and in the ensuing years multiple groups reported 'breaking' the diffraction limit in the far field in both optics and acoustics: sub-diffraction-limited focusing or imaging was observed with metamaterials and without metamaterials, with negative refraction and without negative refraction, with Helmholtz resonators in acoustics and with Maxwell's fish eye lenses in optics [12][13][14][15][16][17]. The general mood was expressed by a commentary in Nature Materials entitled "What diffraction limit?"…”

Section:  mentioning

confidence: 99%

Upholding the diffraction limit in the focusing of light and sound

Maznev

Wright

2017

Wave Motion

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The concept of the diffraction limit put forth by Ernst Abbe and others has been an important guiding principle limiting our ability to tightly focus classical waves, such as light and sound, in the far field. In the past decade, numerous reports have described focusing or imaging with light and sound 'below the diffraction limit'. We argue that the diffraction limit defined in a reasonable way, for example in terms of the upper bound on the wave numbers corresponding to the spatial Fourier components of the intensity profile, or in terms of the spot size into which at least 50% of the incident power can be focused, still stands unbroken to this day. We review experimental observations of 'subwavelength' or 'sub-diffraction-limit' focusing, which can be principally broken down into three broad categories: (i) 'super-resolution', i.e. the technique based on the modification of the pupil of the optical system to reduce the width of the central maximum in the intensity distribution at the expense of increasing side bands; (ii) solid immersion lenses, making use of metamaterials with a high effective index; (iii) concentration of intensity by a subwavelength structure such as an antenna. Even though a lot of interesting work has been done along these lines, none of the hitherto performed experiments violated the sensibly defined diffraction limit.

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Experimental and Theoretical Evidence for Subwavelength Imaging in Phononic Crystals

Cited by 280 publications

References 26 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

Effective impedance boundary optimization and its contribution to dipole radiation and radiation pattern control

Upholding the diffraction limit in the focusing of light and sound

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