Experimental Verification of a Negative Index of Refraction

Shelby, Richard A.; Smith, David R.; Schultz, S.

doi:10.1126/science.1058847

Cited by 8,553 publications

(4,634 citation statements)

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“…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 .…”

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confidence: 99%

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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Hyperlenses and metalenses for far-field super-resolution imaging

2012

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“…By opening a small gap, the split-ring resonator exhibits a negative permeability due to the significantly enhanced inductancecapacitance resonance. The combination of split-ring resonator with the Drude response from an array of continuous metallic wire into a two-element system led to the first negative index material (NIM) at microwave frequencies and the rapidly emerging field of metamaterials [4][5][6][7][8][9][10][11] . However, the long-standing question of the possibility to obtain negative magnetic permeability and negative refractive index with an ensemble of singleelement closed rings has remained.…”

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“…However, the long-standing question of the possibility to obtain negative magnetic permeability and negative refractive index with an ensemble of singleelement closed rings has remained. Artificial materials, through the engineering of meta-atoms of micro-and nano-structures, have exhibited electromagnetic properties that are not accessible in naturally occurring materials, such as negative refraction 4,5 , superlensing [6][7][8] , electromagnetic cloaking 9,10 and unique topological effects 11 . Significant efforts have been devoted to scale NIMs down to the optical domain.…”

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Symmetry breaking and optical negative index of closed nanorings

et al. 2012

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Metamaterials have extraordinary abilities, such as imaging beyond the diffraction limit and invisibility. Many metamaterials are based on split-ring structures, however, like atomic orbital currents, it has long been believed that closed rings cannot produce negative refractive index. Here we report a low-loss and polarization-independent negative-index metamaterial made solely of closed metallic nanorings. Using symmetry breaking that negatively couples the discrete nanorings, we measured negative phase delay in our composite 'chess metamaterial'. The formation of an ultra-broad Fano-resonance-induced optical negativeindex band, spanning wavelengths from 1.3 to 2.3 mm, is experimentally observed in this structure. This discrete and mono-particle negative-index approach opens exciting avenues towards symmetry-controlled topological nanophotonics with on-demand linear and nonlinear responses.

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“…[ 11 ] As a consequence, to meet the requirement of label-free, coupler-free, scalable and intracellular bio-imaging, here we present a plasmonic microscopic platform by employing multimode resonances in spilt-ring resonators (SRRs). The SRRs are artifi cially constructed sub-wavelength structures, which allows negative magnetic permeability, [ 12 ] high-frequency magnetism [ 13 ] and other unprecedented electromagnetic properties [14][15][16] based on their collective plasmonic resonances. In fact, the resonance condition of the SRR signifi cantly depends on their local dielectric environment, so that the SRRs can be readily employed as refractive-index (RI) sensors.…”

Section: Doi: 101002/adma201200291mentioning

confidence: 99%