Absorption and optimal plasmonic resonances for small ellipsoidal particles in lossy media

Dalarsson, Mariana and Nordebo, Sven and Sjöberg, Daniel and Bayford, Richard (2017) Absorption and optimal plasmonic resonances for small ellipsoidal particles in lossy media. Journal of Physics D: Applied Physics, 50 (34). ISSN 0022-3727

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Abstract

A new simplified formula is derived for the absorption cross section of small dielectric ellipsoidal particles embedded in lossy media. The new expression leads directly to a closed form solution for the optimal conjugate match with respect to the surrounding medium, i.e. the optimal permittivity of the ellipsoidal particle that maximizes the absorption at any given frequency. This defines the optimal plasmonic resonance for the ellipsoid. The optimal conjugate match represents a metamaterial in the sense that the corresponding optimal permittivity function may have negative real part (inductive properties), and can not in general be implemented as a passive material over a given bandwidth. A necessary and sufficient condition is derived for the feasibility of tuning the Drude model to the optimal conjugate match at a single frequency, and it is found that all the prolate spheroids and some of the (not too flat) oblate spheroids can be tuned into optimal plasmonic resonance at any desired center frequency. Numerical examples are given to illustrate the analysis. Except for the general understanding of plasmonic resonances in lossy media, it is also anticipated that the new results can be useful for feasibility studies with e.g. the radiotherapeutic hyperthermia based methods to treat cancer based on electrophoretic heating in gold nanoparticle suspensions using microwave radiation.

Item Type: Article
Additional Information: Article number = 345401
Research Areas: A. > School of Science and Technology > Natural Sciences > Biophysics and Bioengineering group
Item ID: 22322
Notes on copyright: This is an author-created, un-copyedited version of an article accepted for publication/published in Journal of Physics D: Applied Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6463/aa7c8a
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Depositing User: Richard Bayford
Date Deposited: 03 Aug 2017 13:54
Last Modified: 15 Sep 2018 04:50
URI: http://eprints.mdx.ac.uk/id/eprint/22322

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