Imaging by flat lens using negative refraction

Parimi, Patanjali V.; Lu, W. T.; Vodo, P.; Sridhar, Srinivas

doi:10.1038/426404a

Cited by 536 publications

(289 citation statements)

References 7 publications

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“…[9][10][11][12] These structures usually contain an array of split ring resonators [6,[13][14][15] or dielectric photonic crystals with periodically modulated ε and µ, [2,6,16] which are often complicated to fabricate. To overcome the difficulties, in this paper we predict that negative refraction can take place in a bulk Weyl semimetal (WSM) even without having negative µ and without constructing complicated structure.…”

Section: Introductionmentioning

confidence: 99%

Negative Refraction in Weyl Semimetals

Ukhtary

Nugraha

2017

J. Phys. Soc. Jpn.

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We theoretically propose that Weyl semimetals may exhibit negative refraction at some frequencies close to the plasmon frequency, allowing transverse magnetic (TM) electromagnetic waves with frequencies smaller than the plasmon frequency to propagate in the Weyl semimetals. The idea is justified by the calculation of reflection spectra, in which negative refractive index at such frequencies gives physically correct spectra. In this case, a TM electromagnetic wave incident to the surface of the Weyl semimetal will be bent with a negative angle of refraction. We argue that the negative refractive index at the specified frequencies of the electromagnetic wave is required to conserve the energy of the wave, in which the incident energy should propagate away from the point of incidence.

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Section: Introductionmentioning

confidence: 99%

Negative Refraction in Weyl Semimetals

Ukhtary

Nugraha

2017

J. Phys. Soc. Jpn.

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“…The negative refraction effect in photonic crystals at the frequencies close to the band-gap edges was reported by Notomi in [13,14] and the sub-wavelength imaging using flat lenses formed by photonic crystals was demonstrated both theoretically [15,16,17,18,19] and experimentally [20,21]. Unfortunately, the resolution of such lenses is strictly limited by period of the crystal.…”

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confidence: 95%

Subwavelength imaging at optical frequencies using a transmission device formed by a periodic layered metal-dielectric structure operating in the canalization regime

2006

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Imaging with sub-wavelength resolution using a lens formed by periodic metal-dielectric layered structure is demonstrated. The lens operates in canalization regime as a transmission device and it does not involve negative refraction and amplification of evanescent modes. The thickness of the lens have to be an integer number of half-wavelengths and can be made as large as required for ceratin applications, in contrast to the other sub-wavelength lenses formed by metallic slabs which have to be much smaller than the wavelength. Resolution of λ/20 at 600 nm wavelength is confirmed by numerical simulation for a 300 nm thick structure formed by a periodic stack of 10 nm layers of glass with ǫ = 2 and 5 nm layers of metal-dielectric composite with ǫ = −1. Resolution of λ/60 is predicted for a structure with same thickness, period and operating frequency, but formed by 7.76 nm layers of silicon with ε = 15 and 7.24 nm layers of silver with ε = −14.PACS numbers: 78.20. Ci, 42.30.Wb,41.20.Jb The possibility of imaging with sub-wavelength resolution was first reported by Pendry in 2000 [1]. It was shown that the slab of left-handed material [2], a medium with both negative permittivity and permeability, can create images with nearly unlimited resolution. This idea impeached validity of classical restriction on resolution of imaging systems: diffraction limit and became a starting point for creation of new research area of metamaterials [3], artificial media possessing extraordinary electromagnetic properties usually not available in the natural materials. The idea of Pendry's perfect lens is based on such exotic phenomena observable in left-handed media as backward waves, negative refraction and amplification of evanescent waves. The far-field of a source is focused due to effects of backward waves and negative refraction. The near field of the source, which contains sub-wavelength details, is recovered in the image plane because of the amplification of evanescent modes in the slab. Currently, the samples of left-handed materials are created only in microwave region [4]. The creation of lefthanded materials at THz frequencies and in optical range meets with problems related to the difficulty in getting required magnetic properties [5,6] which have to be created artificially. In the absence of magnetic properties the lenses formed by materials with negative permittivity only (for example, silver at optical frequencies) are still capable to create images with sub-wavelength resolution, but the operation is restricted to p-polarization only and the lens has to be thin as compared to the wavelength [1]. This idea was confirmed by recent experimental results [7] which demonstrated the reality of sub-wavelength imaging using silver slabs in optical frequency range. The resolution of such lenses is restricted by losses in the silver, but this problem can be alleviated by cutting the slab into the multiple thin layers [8,9] and introduction of active materials [10]. Unfortunately, at the moment there is no recipe how to incre...

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“…Photonic crystals can provide the negative refraction needed for a flat lens, 9 as demonstrated experimentally. 10,11 The electronic analog of a Veselago lens was proposed in the context of graphene 12 based on the negative refraction of an electron crossing from the conduction band into the valence band. Such interband crossing requires a p-n junction, which is highly resistive if the interface extends over more than an electron wavelength.…”

Section: Introductionmentioning

confidence: 99%

Flat-lens focusing of electrons on the surface of a topological insulator

2010

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We propose the implementation of an electronic Veselago lens on the conducting surface of a threedimensional topological insulator ͑such as Bi 2 Te 3 ͒. The negative refraction needed for such a flat lens results from the sign change in the curvature of the Fermi surface, changing from a circular to a snowflakelike shape across a sufficiently large electrostatic potential step. No interband transition ͑as in graphene͒ is needed. For this reason, and because the topological insulator provides protection against backscattering, the potential step is able to focus a broad range of incident angles. We calculate the quantum interference pattern produced by a point source, generalizing the analogous optical calculation to include the effect of a noncircular Fermi surface ͑having a nonzero conic constant͒.

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Imaging by flat lens using negative refraction

Cited by 536 publications

References 7 publications

Negative Refraction in Weyl Semimetals

Negative Refraction in Weyl Semimetals

Subwavelength imaging at optical frequencies using a transmission device formed by a periodic layered metal-dielectric structure operating in the canalization regime

Flat-lens focusing of electrons on the surface of a topological insulator

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