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Mind the gap: testing the Rayleigh hypothesis in T-matrix calculations with adjacent spheroids

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journal contribution
posted on 15.07.2020 by D Schebarchov, EC Le Ru, Johan Grand, Baptiste Auguié
The T-matrix framework offers accurate and efficient modelling of electromagnetic scattering by nonspherical particles in a wide variety of applications ranging from nano-optics to atmospheric science. Its analytical setting, in contrast to purely numerical methods, also provides a fertile ground for further theoretical developments. Perhaps the main purported limitation of the method, when extended to systems of multiple particles, is the often-stated requirement that the smallest circumscribed spheres of neighbouring scatterers not overlap. We consider here such a scenario with two adjacent spheroids whose aspect ratio we vary to control the overlap of the smallest circumscribed spheres, and compute far-field cross-sections and near-field intensities using the superposition T-matrix method. The results correctly converge far beyond the no-overlap condition, and although numerical instabilities appear for the most extreme cases of overlap, requiring high multipole orders, convergence can still be obtained by switching to quadruple precision. Local fields converge wherever the Rayleigh hypothesis is valid for each single scatterer and, remarkably, even in parts of the overlap region. Our results are validated against finite-element calculations, and the agreement demonstrates that the superposition T-matrix method is more robust and broadly applicable than generally assumed.

Funding

Probing the optical absorption of molecules adsorbed on metallic nanoparticles | Funder: Royal Society of New Zealand | Grant ID: 16-VUW-035

History

Preferred citation

(2019). Mind the gap: testing the Rayleigh hypothesis in T-matrix calculations with adjacent spheroids. Opt. Express, 27(24), 35750-35760. https://doi.org/10.1364/OE.27.035750

Journal title

Opt. Express

Volume

27

Issue

24

Publication date

01/11/2019

Pagination

35750-35760

Publisher

OSA

Publication status

Published

Online publication date

20/11/2019

ISSN

1094-4087

eISSN

1094-4087

Article number

24

Language

en

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