Absorption spectrum of clusters of spheres from the general solution of Maxwell's equations. II. Optical properties of aggregated metal spheres

Gerardy, J; Ausloos, Marcel

doi:10.1103/physrevb.25.4204

Cited by 217 publications

(136 citation statements)

References 22 publications

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“…It is thus not surprising that similar optical behavior is observed in experimental dimers and linear chains 40,42,60−64 and is also seen in similar particle−particle electrodynamic calculations on nanopairs and chain assemblies. 55,65,66 While the coinciding resonance energies of straight nanochains and compositionally similar aggregates have been noted previously, 38,49,55 only recently did we discuss how these apparent chain modes are both supported and distributed within the large fractal motif of large three-dimensional (3D) aggregates. 67 Hence, we first discuss this explanation before using it to develop a simple effective composite dipole model for the aggregation process.…”

Section: ■ Introductionmentioning

confidence: 99%

Simple Composite Dipole Model for the Optical Modes of Strongly-Coupled Plasmonic Nanoparticle Aggregates

et al. 2012

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Self-assembled strongly coupled plasmonic aggregates exhibit optical spectra which show complex plasmonic resonances. To understand the optics of such systems, we introduce an effective composite dipole model extending previous effective models of aggregates into the plasmonic domain. The ingredients in this model are found by comparing the time-resolved extinction of self-assembling growing aggregates of gold nanoparticles spaced by rigid sub-nm gaps to recent rigorous electromagnetic simulations of this geometry. The highly reproducible spectral signatures from experiments match our simulations, confirming that the electromagnetic response of such fractal plasmonic clusters can be well-understood in terms of embedded straight chains of plasmonically coupled nanoparticles surrounded by an optically decoupled halo of dimers. We show how to derive simple analytical formulas that lead to rapid extraction of key parameters from such experimental spectra and which properly account for the long-wavelength lineshapes. In particular, we find these effective parameters describe the extent of plasmon delocalization along such chains, the eccentricity of these optically dominant cores, and the fraction of nanoparticles active within them. This underpins applications which depend on spectral selectivity and field enhancements in such tightly coupled plasmonic systems.

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Section: ■ Introductionmentioning

confidence: 99%

Simple Composite Dipole Model for the Optical Modes of Strongly-Coupled Plasmonic Nanoparticle Aggregates

et al. 2012

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“…The observed trend in E L,T is in qualitative agreement with Mie-theory calculations for silver nanoparticle chains in air. 9,10 Figure 3͑a͒ also shows the results of the FDTD simulations described herein ͑black stars͒. In order to model the presence of the glass substrate (nϭ1.5) in the simulations, the medium surrounding the particles was taken to have an effective refractive index nϭ1.2 for the transverse mode.…”

mentioning

confidence: 99%

Observation of coupled plasmon-polariton modes in Au nanoparticle chain waveguides of different lengths: Estimation of waveguide loss

Maier

Kik

Atwater

2002

Applied Physics Letters

486

429

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Near-field interactions between closely spaced Au nanoparticles were characterized by studying the spectral position of the extinction bands corresponding to longitudinal (L) and transverse (T) plasmon-polariton modes of Au nanoparticle chains. Far-field spectroscopy and finite-difference time-domain simulations on arrays of 50 nm diameter Au spheres with an interparticle spacing of 75 nm both show a splitting ⌬E between the L and T modes that increases with chain length and saturates at a length of seven particles at ⌬Eϭ65 meV. We show that the measured splitting will result in a propagation loss of 3 dB/15 nm for energy transport. Calculations indicate that this loss can be reduced by at least one order of magnitude by modifying the shape of the constituent particles. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1503870͔In a recent paper, a method was proposed for guiding electromagnetic energy below the diffraction limit at visible frequencies using ordered arrays of closely spaced noble metal nanoparticles. 1 Energy transport in these plasmon waveguides relies on near-field coupling between surface plasmon-polariton modes of neighboring particles. In contrast to conventional optical waveguides, the minimum size of the guided modes is not limited by the diffraction limit /2n of light, enabling the fabrication of nanoscale optical devices. This type of guiding due to near-field coupling was recently demonstrated experimentally in macroscopic structures operating in the microwave regime. 2 At the submicron scale, a theoretical analysis of plasmon waveguides was done using a point-dipole model, allowing for the determination of the dispersion relation (k) and group velocities v g for energy transport. 3,4 The predictions of the point-dipole model for the collective ͑in-phase͒ excitation of the longwavelength mode ͑wavevector kϭ0͒ of plasmon waveguides consisting of 80 Au nanoparticles were confirmed using farfield spectroscopy. 5 Energy transport in plasmon waveguides relies on the excitation of modes with a finite wave vector (k 0). The functional form (k), the group velocity, and the energy propagation loss all depend on the number of directly interacting nanoparticles. In this letter, we investigate this optical near-field interaction range via a determination of the collective plasmon resonance frequencies for structures with 3, 5, and 7 Au nanoparticles using finite-difference time-domain ͑FDTD͒ simulations. The results are compared with far-field extinction measurements on arrays of plasmon waveguides fabricated using electron-beam lithography. Additionally, a simple mathematical formula is deduced relating the far-field extinction data and the expected waveguide loss.Figure 1 outlines our simulation approach for the determination of the surface plasmon resonance energies E L,T of nanoparticles in plasmon waveguides, where L and T correspond to polarization along ͑longitudinal mode L͒ or perpendicular ͑transverse mode T͒ to the chain axis. The simulation volume is chosen as a rectangular box of di...

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“…The generalized multiparticle Mie theory 34 , 35 consists on expanding the incident (E 0 ), scattered (E S ) and internal (E I ) fields in series of vector spherical harmonics m pq1 (3) and n pq1 (3) defined with respect to the center of the particle i. …”

Section: Methodsmentioning

confidence: 99%

Dark Modes and Fano Resonances in Plasmonic Clusters Excited by Cylindrical Vector Beams

2012

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Control of the polarization distribution of light allows tailoring the electromagnetic response of plasmonic particles. By rigorously extending the generalized multiparticle Mie theory, we show that focused cylindrical vector beams (CVB) can be used to efficiently excite dark plasmon modes in nanoparticle clusters. In addition to the small radiative damping and large field enhancement associated to dark modes, excitation with CVB can give place to unusual phenomenology like the formation of electromagnetic cold spots and the generation of Fano resonances in highly symmetric clusters. Overall, the results show the potential of CVB to tailor the plasmonic response of nanoparticle clusters in a unique way.

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Absorption spectrum of clusters of spheres from the general solution of Maxwell's equations. II. Optical properties of aggregated metal spheres

Cited by 217 publications

References 22 publications

Simple Composite Dipole Model for the Optical Modes of Strongly-Coupled Plasmonic Nanoparticle Aggregates

Simple Composite Dipole Model for the Optical Modes of Strongly-Coupled Plasmonic Nanoparticle Aggregates

Observation of coupled plasmon-polariton modes in Au nanoparticle chain waveguides of different lengths: Estimation of waveguide loss

Dark Modes and Fano Resonances in Plasmonic Clusters Excited by Cylindrical Vector Beams

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