Fanoshells: Nanoparticles with Built-in Fano Resonances

Mukherjee, Shaunak; Sobhani, Heidar; Lassiter, J. Britt; Bardhan, Rizia; Nordlander, Peter; Halas, Naomi J.

doi:10.1021/nl1016392

Cited by 293 publications

(347 citation statements)

References 47 publications

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“…We see that γ 2 = 0 (and so κ 2 = d 2 = 0). So, in this basis, resonance A 1 radiates, but resonance A 2 does not; this is exactly the subradiant-superradiant model 17,19,21,47,48 .…”

Section: Introductionmentioning

confidence: 86%

“…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. However, the general criteria for observing such scattering dark states remain unclear.…”

mentioning

confidence: 99%

“…The interference between multiple resonances in multiple channels may lead to even richer phenomena 11,17,39,67 . …”

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confidence: 99%

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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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“…We see that γ 2 = 0 (and so κ 2 = d 2 = 0). So, in this basis, resonance A 1 radiates, but resonance A 2 does not; this is exactly the subradiant-superradiant model 17,19,21,47,48 .…”

Section: Introductionmentioning

confidence: 86%

mentioning

confidence: 99%

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Theoretical Criteria for Scattering Dark States in Nanostructured Particles

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“…24 There are also examples from plasmonicnanomaterial optics where several coupled oscillators are used to reproduce Fano-like spectra. [25][26][27] …”

Section: B Frequency-domain Responsementioning

confidence: 99%

Classical Fano oscillator

Riffe

2011

Phys. Rev. B

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Starting from the quantum-mechanical Fano-Anderson Hamiltonian, we derive classical equations of motion for coordinates associated with the discrete and continuum states. The frequency-dependent absorption spectrum associated with this classical system exhibits the same Fano line shape as the quantum-mechanical system when appropriate correspondences between classical and quantum variables are made. In the time domain, the response of this classical Fano oscillator depends upon the asymmetry parameter q that appears in the expression for the Fano line shape. In particular, under the influence of impulsive driving of the system, the discrete oscillator's phase changes by ±π/2 as q increases from zero (maximum asymmetry in the frequency domain) to ∓∞ (minimum asymmetry). Previously published ultrafast-laser-pulse-driven coherent-phonon oscillations in degenerate p-type Si [K. Kato et al., Jpn. J. Appl. Phys. 48, 100205 (2009)] are discussed in light of these theoretical results.

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“…An alternative widely studied structure for generation of plasmonic FR are core-shell single particles, that have isotropic optical response and can be synthesized by large-throughput and cost-efficient chemical methods. The electromagnetic response of core-shell particles has been largely investigated since this system enables achieving total scattering cancellation and hence represents a canonical example of cloacking device 23 .. Multi-layered coreshell particles can give place to FR arising from the interaction between hybridized modes that result from the coupling of plasmons excited at different metal-dielectric interfaces [24][25][26] . Additional FR can be also observed in non-concentric core-shell particles 24,[27][28][29] , since symmetry breaking induces electromagnetic coupling between otherwise non-interacting orthogonal modes 30 .…”

Section: Introductionmentioning

confidence: 99%

Boosting Fano resonances in single layered concentric core–shell particles

Sancho‐Parramon

Jelovina

2014

Nanoscale

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Efficient excitation of Fano resonances in plasmonic systems usually requires complex nano-structure geometries and some degree of symmetry breaking. However, a single-layer concentric core-shell particle presents inherent Fano profiles in the scattering spectra when sphere and cavity modes spectrally overlap. Weak hybridization and proper choice of core and shell materials gives place to strong electric dipolar Fano resonances in these systems and retardation effects can result in resonances of higher multipolar order or of magnetic type. Furthermore, proper tailoring of illumination conditions leads to an enhancement of the Fano resonance by quenching of unwanted electromagnetic modes. Overall, it is shown that single layer core-shell particles can act as robust Fano resonators.

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Fanoshells: Nanoparticles with Built-in Fano Resonances

Cited by 293 publications

References 47 publications

Theoretical Criteria for Scattering Dark States in Nanostructured Particles

Theoretical Criteria for Scattering Dark States in Nanostructured Particles

Classical Fano oscillator

Boosting Fano resonances in single layered concentric core–shell particles

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