Negative refraction and focusing of elastic Lamb waves at an interface

Bramhavar, Suraj; Prada, Claire; Maznev, A. A.; Every, A. G.; Norris, Theodore B.; Murray, Todd W.

doi:10.1103/physrevb.83.014106

Cited by 79 publications

(60 citation statements)

References 25 publications

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“…[19][20][21][22] An elastic analog of graphene has not been fully analyzed, although the effort to create structures to control the propagation of elastic waves in 2D systems has been remarkable. Thus phononic band-gap systems for Lamb waves have been widely studied, [23][24][25][26][27] as well as advanced refractive structures [28][29][30] or more complex devices based on the transformation-coordinate method. [31][32][33] This work presents an elastic analog of graphene.…”

Section: Introductionmentioning

confidence: 99%

Elastic analog of graphene: Dirac cones and edge states for flexural waves in thin plates

2013

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An elastic analog of graphene is introduced and analyzed. The system consists of a honeycomb arrangement of spring-mass resonators attached to a thin elastic layer, and the propagation properties of flexural waves along it is studied. The band-structure calculation shows the presence of Dirac points near the K point of the Brillouin zone. Analytical expressions are found for both Dirac frequency and velocity as a function of the resonator's parameters. Finally, the bounded modes of infinitely long ribbons of this honeycomb arrangement are analyzed. The presence of edge states, which are studied using multiple scattering theory, is shown. It is concluded that these structures can be used to control the propagation of flexural waves in thin plates.

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Section: Introductionmentioning

confidence: 99%

Elastic analog of graphene: Dirac cones and edge states for flexural waves in thin plates

2013

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“…The lattice constant is 0.34 l at 10 kHz and the dispersion band is used to generate NR and achieve focusing. A NR of Lamb waves was demonstrated by conversion between forward-and backward-propagating modes at the interface where the plate thickness changes 26 .…”

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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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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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“…The near-field 'superlens' and the far-field 'Veselago lens' are two different phenomena: the latter only requires that both  and be negative and their product be unity, resulting in n=-1 (assuming that the second medium is vacuum with n=1) [8]. Furthermore, the group velocity opposite to the phase velocity, which leads to 'Veselago focusing' via negative refraction, is encountered in systems without double negativity [10]. Pendry's ideal superlens effect, on the other hand, is specific to the case of a lossless double-negative medium with  = =-1.…”

Section: Introductionmentioning

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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Negative refraction and focusing of elastic Lamb waves at an interface

Cited by 79 publications

References 25 publications

Elastic analog of graphene: Dirac cones and edge states for flexural waves in thin plates

Elastic analog of graphene: Dirac cones and edge states for flexural waves in thin plates

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

Upholding the diffraction limit in the focusing of light and sound

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