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Whispering gallery mode single nanoparticle detection and sizing: the validity of the dipole approximation

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Title: Whispering gallery mode single nanoparticle detection and sizing: the validity of the dipole approximation
Authors: Foreman, MR
Keng, D
Treasurer, E
Lopez, JR
Arnold, S
Item Type: Journal Article
Abstract: Interactions between whispering gallery modes (WGMs) and small nanoparticles are commonly modeled by treating the particle as a point dipole scatterer. This approach is assumed to be accurate as long as the nanoparticle radius, , is small compared to the WGM wavelength . In this Letter, however, we show that the large field gradients associated with the evanescent decay of a WGM causes the dipole theory to significantly underestimate the interaction strength and, hence, the induced WGM resonance shift, even for particles as small as ∼ /10. To mitigate this issue, we employ a renormalized Born approximation to more accurately determine nanoparticle-induced resonance shifts and, hence, enable improved particle sizing. The domain of validity of this approximation is investigated, and supporting experimental results are presented.
Issue Date: 27-Feb-2017
Date of Acceptance: 8-Feb-2017
URI: http://hdl.handle.net/10044/1/44513
DOI: https://dx.doi.org/10.1364/OL.42.000963
ISSN: 1539-4794
Publisher: Optical Society of America
Start Page: 963
End Page: 966
Journal / Book Title: Optics Letters
Volume: 42
Issue: 5
Copyright Statement: © 2017 Optical Society of America
Sponsor/Funder: Royal Society
Funder's Grant Number: University Research Fellowship
Keywords: Optics
0205 Optical Physics
0206 Quantum Physics
0906 Electrical And Electronic Engineering
Publication Status: Published
Appears in Collections:Physics
Photonics
Faculty of Natural Sciences



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