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Point-dipole approximation for small systems of strongly coupled radiating nanorods
Derek W Watson1, Stewart D Jenkins2, Vassili A Fedotov3
1Mathematical Sciences and Centre for Photonic Metamaterials, University of Southampton, Southampton, SO17 1BJ, United Kingdom. derek.w.watson@gmail.com.
Scientific Reports
|April 7, 2019
Summary
Point dipole approximations accurately model plasmonic nanorods when separated by specific distances. Closer spacing requires considering finite-size effects for accurate excitation mode analysis.
Area of Science:
- Plasmonics and Nanophotonics
- Computational Electromagnetics
- Metamaterials
Background:
- Closely-spaced resonators exhibit strong coupling via scattered electromagnetic fields.
- Collective interactions dominate system response in large resonator ensembles.
- Point-dipole approximations offer computational efficiency for large systems.
Purpose of the Study:
- To investigate the validity of point-dipole approximations in small systems of strongly coupled plasmonic nanorods.
- To analyze the influence of resonator separation on super-radiant and subradiant excitations.
- To develop simplified effective models for coupled nanorod systems.
Main Methods:
- Detailed theoretical study of strongly coupled plasmonic nanorods.
- Analysis of point-dipole approximation accuracy across various rod lengths and separations.
- Construction of effective metamolecule models for pairs of nanorods.
Main Results:
- Point-dipole approximation is accurate for nanorod lengths around 210 nm when the separation parameter 'kl' satisfies a specific condition.
- Finite-size and geometry effects significantly alter excitation modes at smaller separations.
- Cooperative mode line shifts diverge rapidly as resonator separation decreases.
Conclusions:
- The point-dipole approximation has a limited range of validity for strongly coupled plasmonic nanorods.
- Accurate modeling of closely spaced nanorods necessitates accounting for their finite size and geometry.
- Effective metamolecule models provide a simplified approach for understanding coupled nanorod behavior.
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