Plasmonic atoms and plasmonic molecules

Климов, В. В.; Гузатов, Д. В.

doi:10.1007/s00339-007-4115-5

Cited by 45 publications

(51 citation statements)

References 40 publications

(39 reference statements)

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“…For modes that involve the outer region to leading order, the outer problem could be reduced via matching to a regularised problem that is amenable to a straightforward numerical solution. Further generalisations of interest would be clusters of more than two closely spaced plasmonic particles [34,50] and periodic arrangements of nearly touching particles [15,51]. Matched asymptotic expansions could also be used to study other types of nearly singular geometries such as elongated nanorods [29].…”

Section: Discussionmentioning

confidence: 99%

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Asymptotic approximations for the plasmon resonances of nearly touching spheres

Schnitzer

2019

Eur. J. Appl. Math

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Excitation of surface-plasmon resonances of closely spaced nanometallic structures is a key technique used in nanoplasmonics to control light on subwavelength scales and generate highly confined electric-field hotspots. In this paper we develop asymptotic approximations in the near-contact limit for the entire set of surface-plasmon modes associated with the prototypical sphere dimer geometry. Starting from the quasi-static plasmonic eigenvalue problem, we employ the method of matched asymptotic expansions between a gap region, where the boundaries are approximately paraboloidal, pole regions within the spheres and close to the gap, and a particle-scale region where the spheres appear to touch at leading order. For those modes that are strongly localised to the gap, relating the gap and pole regions gives a set of effective eigenvalue problems formulated over a half space representing one of the poles. We solve these problems using integral transforms, finding asymptotic approximations, singular in the dimensionless gap width, for the eigenvalues and eigenfunctions. In the special case of modes that are both axisymmetric and odd about the plane bisecting the gap, where matching with the outer region introduces a logarithmic dependence upon the dimensionless gap width, our analysis follows [O. Schnitzer, Physical Review B, 92 235428 2015]. We also analyse the so-called anomalous family of even modes, characterised by field distributions excluded from the gap. We demonstrate excellent agreement between our asymptotic formulae and exact calculations.

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Section: Discussionmentioning

confidence: 99%

“…Consider next the gap-localised even modes. Our approximation for the eigenvalues (115) is equivalent to the approximation obtained by Klimov and coworkers [15,34], only that their result is given in terms of an infinite series. We now see that the latter series is nothing but the…”

Section: Approximations In the Literaturementioning

confidence: 91%

Asymptotic approximations for the plasmon resonances of nearly touching spheres

Schnitzer

2019

Eur. J. Appl. Math

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“…This attributes to the intrinsic property of graphene and therefore independent with graphene structures [47,53]. The absorption enhancement can be explained by considering that in the absence of 8 quenching, increasing the number of carriers effectively increases the probability of virtual electron-hole pair transition by photon absorption.…”

Section: (B) and 4(c)mentioning

confidence: 99%

“…We demonstrate enhancement of graphene absorption over a broad frequency band (0.5-60 THz) with an average absorption level exceeding 20%. Owing to the continuous nature of the metasurface patterns, both absorption level and bandwidth can be controlled electrically by varying the graphene charge carrier concentration.Keywords: graphene plasmonics, fractal metasurfaces, broadband absorber 2 Structuring materials [1][2][3][4] at the subwavelength scale has led to the emergence of metamaterials [5][6][7], a paradigm shift in the design of artificial electromagnetic materials [8] resulting in technologically important, as well as exotic, applications, including perfect lenses [9], transformation optics and invisibility cloaks [10], and perfect absorbers [11]. The properties of metamaterials largely arise from resonant dispersion; hence material loss restricts the strength [12] and bandwidth of the metamaterial response [13].…”

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confidence: 99%

Self-Affine Graphene Metasurfaces for Tunable Broadband Absorption

Papasimakis

Tsai

2016

Phys. Rev. Applied

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Graphene has emerged as a promising platform for THz metasurfaces supporting electrically tunable deep-subwavelength plasmonic excitations. Here, we introduce a broadband graphene metasurface based on the Hilbert curve, a continuous, space-filling fractal. We demonstrate enhancement of graphene absorption over a broad frequency band (0.5-60 THz) with an average absorption level exceeding 20%. Owing to the continuous nature of the metasurface patterns, both absorption level and bandwidth can be controlled electrically by varying the graphene charge carrier concentration.Keywords: graphene plasmonics, fractal metasurfaces, broadband absorber 2 Structuring materials [1][2][3][4] at the subwavelength scale has led to the emergence of metamaterials [5][6][7], a paradigm shift in the design of artificial electromagnetic materials [8] resulting in technologically important, as well as exotic, applications, including perfect lenses [9], transformation optics and invisibility cloaks [10], and perfect absorbers [11]. The properties of metamaterials largely arise from resonant dispersion; hence material loss restricts the strength [12] and bandwidth of the metamaterial response [13].In particular, with respect to perfect absorbers, various schemes have been suggested in order to achieve strong absorption in gigahertz [14] [25]. However, such methods often result in complex, bulky configurations, with little tunability. Graphene, a monolayer of carbon atoms, provides an appealing alternative: owing to its band structure, graphene supports plasmonic excitations at the deep sub-wavelength scale [26]. Plasmonic resonators can be realized by structuring graphene at the nanoscale [27][28][29], which can then be employed to construct graphene metasurfaces targeting the THz part of the spectrum [30][31][32][33][34]. At the same time the high sensitivity of the electromagnetic properties of graphene to the charge carrier [35] concentration provides means of electrical control of plasmons [36][37][38]. In 3 addition to tunability, graphene as a plasmonic material allows to strongly confine electromagnetic radiation to much smaller physical volumes compared to typical metals.For example, the plasmon wavelength for graphene is about 50 times smaller than the free-space wavelength, while for noble metals this is an order of magnitude smaller [26,29]. Such strong field confinement allows people to realize very complex graphene structures while retaining a subwavelength footprint. Graphene exhibits broadband nonlinearities and high thermal conductivity, whereas its atomic thickness facilitates device integration.Here, we introduce fractal graphene metasurfaces as tunable, broadband THz absorbers of monoatomic thickness (see Fig. 1(a)). We demonstrate multifold enhancement of absorption over an extremely broad frequency band, where average absorption levels exceed 20% from 0.5 to 60 THz in strongly doped graphene. We show that the absorption band is strongly dependent on the charge carrier concentration enabling dynamic electrosta...

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“…In dimers, i.e. systems consisting of two particles, in the case of small losses and small distances between the particles, an essentially new type of localized oscillations ("plasmonic molecules") can be seen [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Loss compensation symmetry in dimers made of gain and lossy nanoparticles

et al. 2018

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The eigenoscillations in a two-dimensional dimer made of gain and lossy nanoparticles were investigated within exact analytical approach. It was shown that there are eigenoscillations for which all Joule losses are exactly compensated by the gain. Among such solutions, there are solutions with a new type of symmetry, which we refer to as Loss Compensation Symmetry (LCS) as well as well-known PT (parity-time) symmetric solutions. The modes with LCS unlike PT symmetric ones allow one to achieve full loss compensation with significantly less gain that in the case of PT symmetry. This effect paves way to the new loss compensation methods in optics.

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Plasmonic atoms and plasmonic molecules

Cited by 45 publications

References 40 publications

Asymptotic approximations for the plasmon resonances of nearly touching spheres

Asymptotic approximations for the plasmon resonances of nearly touching spheres

Self-Affine Graphene Metasurfaces for Tunable Broadband Absorption

Loss compensation symmetry in dimers made of gain and lossy nanoparticles

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