Far-field sub-wavelength imaging and focusing using a wire medium based resonant metalens

Lemoult, Fabrice; Fink, Mathias; Lerosey, Geoffroy

doi:10.1080/17455030.2011.613954

Cited by 48 publications

(30 citation statements)

References 28 publications

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“…In the following, we explain, based on the soda can metamaterial example, how and under which conditions they can indeed be used. The reader has to keep in mind that the soda can medium is a very good airborne acoustic example for this study which has been published in [25], but similar results have been obtained in underwater acoustics in the ultrasonic range with a bubble as a unit cell [44], with Lamb waves in a thin plate [45], in electromagnetics in the microwave regime [27,46], and in the optical range [47,48], making this approach very robust and general.…”

Section: Subwavelength Focusing In the Context Of Metamaterialsmentioning

confidence: 80%

Soda Cans Metamaterial: A Subwavelength-Scaled Phononic Crystal

et al. 2016

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Photonic or phononic crystals and metamaterials, due to their very different typical spatial scales-wavelength and deep subwavelength-and underlying physical mechanisms-Bragg interferences or local resonances-, are often considered to be very different composite media. As such, while the former are commonly used to manipulate and control waves at the scale of the unit cell, i.e., wavelength, the latter are usually considered for their effective properties. Yet we have shown in the last few years that under some approximations, metamaterials can be used as photonic or phononic crystals, with the great advantage that they are much more compact. In this review, we will concentrate on metamaterials made out of soda cans, that is, Helmholtz resonators of deep subwavelength dimensions. We will first show that their properties can be understood, likewise phononic crystals, as resulting from interferences only, through multiple scattering effects and Fano interferences. Then, we will demonstrate that below the resonance frequency of its unit cell, a soda can metamaterial supports a band of subwavelength varying modes, which can be excited coherently using time reversal, in order to beat the diffraction limit from the far field. Above this frequency, the metamaterial supports a band gap, which we will use to demonstrate cavities and waveguides, very similar to those obtained in phononic crystals, albeit of deep subwavelength dimensions. We will finally show that multiple scattering can be taken advantage of in these metamaterials, by correctly structuring them. This allows to turn a metamaterial with a single negative effective property into a negative index metamaterial, which refracts waves negatively, hence acting as a superlens.

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Section: Subwavelength Focusing In the Context Of Metamaterialsmentioning

confidence: 80%

Soda Cans Metamaterial: A Subwavelength-Scaled Phononic Crystal

et al. 2016

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“…Alternative approaches have been proposed for sub-diffraction-limited imaging utilizing inversion procedures with far-field detection, including time reversal, optical diffraction tomography (ODT) and compressed sensing [65][66][67][68][69][70] . The time-reversal technique was first introduced as an inversion method for electromagnetic waves and was experimentally demonstrated by subwavelength focusing and imaging of microwaves 65,66,[71][72][73][74][75] . Evanescent waves that carry small details are converted into propagating waves by placing a subwavelength object made of monopoles in the near field of a cluster of strongly coupled resonators, referred to as a 'resonant metalens' (Fig.…”

Section: Extraordinary Imaging Properties Of the Hyperbolic Metalensmentioning

confidence: 99%

“…Based on the reciprocity of the system, not only propagating waves but also evanescent waves can be recovered at the monopole location. An image with a sub-diffraction-limited resolution of l/80 has been reconstructed by cross-correlation between the received signals and the filters 66,72 . An extension to 2D imaging is possible by using a total internal reflection configuration 72 .…”

Section: Extraordinary Imaging Properties Of the Hyperbolic Metalensmentioning

confidence: 99%

“…An image with a sub-diffraction-limited resolution of l/80 has been reconstructed by cross-correlation between the received signals and the filters 66,72 . An extension to 2D imaging is possible by using a total internal reflection configuration 72 . The resolution of such a resonant metalens is affected by the period of the wires, as well as the loss in metals, which cannot be compensated by time reversal.…”

Section: Extraordinary Imaging Properties Of the Hyperbolic Metalensmentioning

confidence: 99%

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Hyperlenses and metalenses for far-field super-resolution imaging

2012

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The resolution of conventional optical lens systems is always hampered by the diffraction limit. Recent developments in artificial metamaterials provide new avenues to build hyperlenses and metalenses that are able to image beyond the diffraction limit. Hyperlenses project super-resolution information to the far field through a magnification mechanism, whereas metalenses not only super-resolve subwavelength details but also enable optical Fourier transforms. Recently, there have been numerous designs for hyperlenses and metalenses, bringing fresh theoretical and experimental advances, though future directions and challenges remain to be overcome.O ptical microscopy has revolutionized many fields such as microelectronics, biology and medicine. However, the resolution of a conventional optical lens system is always limited by diffraction to about half the wavelength of light. This diffraction barrier arises from the fact that subwavelength information from an object is carried by high spatial-frequency evanescent waves, which only exist in the near field. To overcome this diffraction limit, pioneering work has been carried out, including near-field scanning microscopy 1 , as well as fluorescence-based imaging methods 2,3 . These scanning-or random sampling-based nonprojection techniques achieve super-resolving power by sacrificing imaging speed, making them uncompetitive for dynamic imaging.Lens-based projection imaging remains the best option for high-speed microscopy. Immersion techniques have been proposed to enhance resolution, but they are limited by the low refractive indices of natural materials 4 . Emerging within the last decade, the fields of plasmonics and metamaterials provide solutions for engineering extraordinary material properties not found in nature, such as negative index of refraction 5,6 or strongly anisotropic materials 7,8 . This has provided tremendous opportunities for novel lens designs with unprecedented resolution 9 . Initiated by Pendry's seminal concept of the perfect lens 10 , a number of superlenses were demonstrated with resolving powers beyond the diffraction limit [11][12][13][14][15][16][17] . The optical superlens first achieved sub-diffraction-limited resolution by enhancing evanescent waves through a slab of silver 11 . As the evanescent-field enhancement is enabled by surface plasmon excitation, the subwavelength image is typically limited to the near field of the metal slab. However, the hyperlens-a metamaterial-based lens-can send super-resolution images into the far field by introducing a magnification mechanism. This has been considered as one of the most promising candidates for practical applications since its first demonstration in 2007 (refs 13,14). Recently, various other metamaterial-based lenses, that is, metalenses, have also been developed with both

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“…Numerical simulations based on this idea 92 have shown that wavefront shaping can be used to focus monochromatic light to subwavelength spots in an array of split rings. In this monochromatic approach, coupling between resonators gives rise to spatial sidelobes that are suppressed when using polychromatic signals 93,94 .…”

Section: The Medium As the Lensmentioning

confidence: 99%