<i>Ab initio</i>theory of Fano resonances in plasmonic nanostructures and metamaterials

Gallinet, Benjamin; Martin, Olivier J. F.

doi:10.1103/physrevb.83.235427

Cited by 293 publications

(313 citation statements)

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“…[5][6][7][8][9] A particularly interesting phenomenon is the suppressed scattering in nanostructures with multiple plasmonic resonances, [10][11][12][13][14][15][16][17][18][19][20][21][22][23] plasmonic and excitonic resonances, [24][25][26][27][28][29][30] or dielectric resonances, 31,32 referred to collectively as a "scattering dark state." A wealth of models has been employed to describe this suppressed scattering, ranging from perturbative models, 12 generalization of the Fano formula, [13][14][15] and electrostatic approximation, 22,23 to coupled-mechanical-oscillator models. [17][18][19][20][21] These models reveal valuable insights and facilitate the design of specific structures with desired line shapes.…”

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Theoretical Criteria for Scattering Dark States in Nanostructured Particles

et al. 2014

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Nanostructures with multiple resonances can exhibit a suppressed or even completely eliminated scattering of light, called a scattering dark state. We describe this phenomenon with a general treatment of light scattering from a multi-resonant nanostructure that is spherical or non-spherical but subwavelength in size. With multiple resonances in the same channel (i.e. same angular momentum and polarization), coherent interference always leads to scattering dark states in the low-absorption limit, regardless of the system details. The coupling between resonances is inevitable and can be interpreted as arising from far-field or near-field. This is a realization of coupled- and interference effects. 5-9 A particularly interesting phenomenon is the suppressed scattering in nanostructures with multiple plasmonic resonances, [10][11][12][13][14][15][16][17][18][19][20][21][22][23] plasmonic and excitonic resonances, [24][25][26][27][28][29][30] or dielectric resonances, 31,32 referred to collectively as a "scattering dark state." A wealth of models has been employed to describe this suppressed scattering, ranging from perturbative models, 12 generalization of the Fano formula, 13-15 and electrostatic approximation, 22,23 to coupled-mechanical-oscillator models. 17-21 These models reveal valuable insights and facilitate the design of specific structures with desired line shapes. However, the general criteria for observing such scattering dark states remain unclear. Non-scattering states have been known in atomic physics since the early works of Fano 33 and have been discovered in a variety of nanoscale systems in recent years [5][6][7][8]34,35 . However, Fano resonances generally concern the interference between a narrow discrete resonance and a broad resonance or continuum. Meanwhile, many occurrences of the scattering dark state involve the interference between multiple narrow discrete resonances, and it seems necessary to treat the multiple resonances at equal footing. Thus, we seek a formalism analogous to the phenomenon of coupled-resonator-induced transparency 5 that has been established in certain other systems such as coupled mechanical oscillators 36,37 , coupled cavities 38,39 , coupled microring resonators [40][41][42][43][44] , and planar metamaterials [45][46][47][48] .Here, we derive the general equations governing the resonant light scattering from a spherical or a non-spherical but subwavelength obstacle, accounting for multiple resonances with low loss. Due to the spherical symmetry (or the small size) of the obstacle, different channels of the multipole fields are decoupled. We find that within each channel, n resonances always lead to n − 1 scattering dark states in the low-absorption limit. This universal result is independent of the radiative decay rates of the resonances, method of coupling (can be 3 near-field or far-field), nature of the resonances (can be plasmon, exciton, whispering-gallery, etc.), number of resonances, which of the multipole, TE or TM polarization, and other system det...

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Theoretical Criteria for Scattering Dark States in Nanostructured Particles

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“…The resulting reflectance profile is modulated by an asymmetric line shape characteristic of Fano resonances. 16,21,28,29 Around the resonance frequency of the quadrupolar mode ω 0 , the reflectance spectrum R is the product of the antenna reflectance R a by the asymmetric modulation function: 19,29 …”

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Plasmonic Radiance: Probing Structure at the Ångström Scale with Visible Light

et al. 2013

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Plasmonic modes with long radiative lifetimes combine strong nanoscale light confinement with a narrow spectral line width carrying the signature of Fano resonances, making them very promising for nanophotonic applications such as sensing, lasing, and switching. Their coupling to incident radiation, also known as radiance, determines their optical properties and optimal use in applications. In this work, we theoretically and experimentally demonstrate that the radiance of a plasmonic mode can be classified into three different regimes. In the weak coupling regime, the line shape exhibits remarkable sensitivity to the dielectric environment. We show that geometrical displacements and deformations at the Ångstrom scale can be detected optically by measuring the radiance. In the intermediate regime, the electromagnetic energy stored in the mode is maximal, with large electric field enhancements that can be exploited in surface enhanced spectroscopy applications. In the strong coupling regime, the interaction can result in hybridized modes with tunable energies. KEYWORDS: Fano resonances, electromagnetically induced transparency, plasmonic nanosensors, surface enhanced Raman scattering (SERS), extraordinary optical transmission W ith their ability to concentrate light at a deepsubwavelength scale by excitation of surface plasmons, metallic nanostructures play a major role in current nanoscience. 1 In particular, optical tweezers, 2 antennas, 3,4 lasers, 5 photodetectors, 6 or biochemical sensing platforms 7,8 have been scaled down to the nanometer range. However, their performance are limited by the short lifetimes of surface plasmon resonances. 9 Recently, it has been shown that the use of plasmonic modes with long radiative life times (subradiant modes) can drastically enhance the performance of nanophotonic devices. 10−12 Their spectral response carry an asymmetric line shape with sharp spectral features, characteristic of Fano resonances. 13−22 The coupling of subradiant modes to radiation, their radiance, is directly controlled by the geometrical configuration of the nanostructures, 19 and also governs their optical response and the location and amplitude of light confinement. 20 Despite the fact that the use of subradiant modes for nanophotonic applications critically depends on the coupling strength, the choice of an optimal regime has so far never been addressed.In this work, we use a universal model for interacting radiative and localized channels to investigate the radiance of a plasmonic mode. We demonstrate that the radiance of a plasmonic mode can be classified into three different regimes. In the weak coupling regime, the radiance of the mode is small and extremely sensitive to perturbations in the coupling. We introduce a novel sensing concept, radiance sensing, which is based on the sensitivity of the radiance to the environment, rather than conventional plasmon sensing relying on the wavelength shift of plasmon modes. 8 In the intermediate regime, the radiative damping is equal to the int...

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“…A unique nonradiative mode E 0 , defined as the eigenfunction of the projector to nonradiative modes, Q |E 0 ae = |E 0 ae, satisfies the following eigenvalue equation: 16 ( QM Q À ω 2 0 I )jE 0 ae ¼ 0…”

Section: Methodsmentioning

confidence: 99%

Refractive Index Sensing with Subradiant Modes: A Framework To Reduce Losses in Plasmonic Nanostructures

Gallinet

Martin

2013

ACS Nano

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Plasmonic modes with long radiative lifetimes, subradiant modes, combine strong confinement of the electromagnetic energy at the nanoscale with a steep spectral dispersion, which makes them promising for biochemical sensors or immunoassays. Subradiant modes have three decay channels: Ohmic losses, their extrinsic coupling to radiation, and possibly their intrinsic dipole moment. In this work, the performance of subradiant modes for refractive index sensing is studied with a general analytical and numerical approach. We introduce a model for the impact that has different decay channels of subradiant modes on the spectral resolution and contrast. It is shown analytically and verified numerically that there exists an optimal

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Ab initiotheory of Fano resonances in plasmonic nanostructures and metamaterials

Cited by 293 publications

References 30 publications

Theoretical Criteria for Scattering Dark States in Nanostructured Particles

Theoretical Criteria for Scattering Dark States in Nanostructured Particles

Plasmonic Radiance: Probing Structure at the Ångström Scale with Visible Light

Refractive Index Sensing with Subradiant Modes: A Framework To Reduce Losses in Plasmonic Nanostructures

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