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Point-dipole approximation for small systems of strongly coupled radiating nanorods

Point-dipole approximation for small systems of strongly coupled radiating nanorods
Point-dipole approximation for small systems of strongly coupled radiating nanorods

Systems of closely-spaced resonators can be strongly coupled by interactions mediated by scattered electromagnetic fields. In large systems the resulting response has been shown to be more sensitive to these collective interactions than to the detailed structure of individual resonators. Attempts to describe such systems have resulted in point-dipole approximations to resonators that are computationally efficient for large resonator ensembles. Here we provide a detailed study for the validity of point dipole approximations in small systems of strongly coupled plasmonic nanorods, including the cases of both super-radiant and subradiant excitations, where the characteristics of the excitation depends on the spatial separation between the nanorods. We show that over an appreciable range of rod lengths centered on 210 nm, when the relative separation kl in terms of the resonance wave number of light k satisfies kl≳ π/ 2 , the point electric dipole model becomes accurate. However, when the resonators are closer, the finite-size and geometry of the resonators modifies the excitation modes, in particular the cooperative mode line shifts of the point dipole approximation begin to rapidly diverge at small separations. We also construct simplified effective models by describing a pair of nanorods as a single effective metamolecule.

2045-2322
Watson, Derek W.
4cb78431-9921-4c6e-9d68-0e8eaa3628e5
Jenkins, Stewart D.
65d861fb-b85a-4927-805a-7c906fca26c6
Fedotov, Vassili A.
3725f5cc-2d0b-4e61-95c5-26d187c84f25
Ruostekoski, Janne
2beb155e-64b0-4ee9-9cfe-079947a9c9f4
Watson, Derek W.
4cb78431-9921-4c6e-9d68-0e8eaa3628e5
Jenkins, Stewart D.
65d861fb-b85a-4927-805a-7c906fca26c6
Fedotov, Vassili A.
3725f5cc-2d0b-4e61-95c5-26d187c84f25
Ruostekoski, Janne
2beb155e-64b0-4ee9-9cfe-079947a9c9f4

Watson, Derek W., Jenkins, Stewart D., Fedotov, Vassili A. and Ruostekoski, Janne (2019) Point-dipole approximation for small systems of strongly coupled radiating nanorods. Scientific Reports, 9 (1). (doi:10.1038/s41598-019-41327-6).

Record type: Article

Abstract

Systems of closely-spaced resonators can be strongly coupled by interactions mediated by scattered electromagnetic fields. In large systems the resulting response has been shown to be more sensitive to these collective interactions than to the detailed structure of individual resonators. Attempts to describe such systems have resulted in point-dipole approximations to resonators that are computationally efficient for large resonator ensembles. Here we provide a detailed study for the validity of point dipole approximations in small systems of strongly coupled plasmonic nanorods, including the cases of both super-radiant and subradiant excitations, where the characteristics of the excitation depends on the spatial separation between the nanorods. We show that over an appreciable range of rod lengths centered on 210 nm, when the relative separation kl in terms of the resonance wave number of light k satisfies kl≳ π/ 2 , the point electric dipole model becomes accurate. However, when the resonators are closer, the finite-size and geometry of the resonators modifies the excitation modes, in particular the cooperative mode line shifts of the point dipole approximation begin to rapidly diverge at small separations. We also construct simplified effective models by describing a pair of nanorods as a single effective metamolecule.

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Accepted/In Press date: 21 February 2019
e-pub ahead of print date: 5 April 2019

Identifiers

Local EPrints ID: 430442
URI: https://eprints.soton.ac.uk/id/eprint/430442
ISSN: 2045-2322
PURE UUID: 0e2e1947-ad5f-478a-b746-d2ad54b39ad4

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Date deposited: 01 May 2019 16:30
Last modified: 19 Jul 2019 16:35

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Contributors

Author: Derek W. Watson
Author: Stewart D. Jenkins

University divisions

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