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Optical cavity modes in gold shell colloids

Penninkhof, J. J. and Sweatlock, L. A. and Moroz, A. and Atwater, H. A. and van Blaaderen, A. and Polman, A. (2008) Optical cavity modes in gold shell colloids. Journal of Applied Physics, 103 (12). Art. No. 123105. ISSN 0021-8979. http://resolver.caltech.edu/CaltechAUTHORS:PENjap08

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Abstract

Core-shell colloids composed of a dielectric core surrounded by a metal shell show geometric cavity resonances with optical properties that are distinctly different than those of the collective plasmon modes of the metal shell. We use finite-difference time domain calculations on silica colloids with a core diameter of 456 nm, surrounded by a 38 nm thick Au shell, to study the temporal evolution of the mode field intensity inside the cavity upon pulsed excitation. Calculations using Mie theory and the T-matrix method are used to analytically determine the dipolar cavity resonance spectrum, which is found superimposed on the broad collective dipolar plasmonic resonance modes. We characterize resonance wavelength and linewidth in terms of a geometric mode confined inside the cavity. Cavity linewidth can be controlled by metal shell thickness and quality factors Q>150 are observed. Due to the small cavity mode volume V=0.2(lambda/n)^3, a Purcell factor as high as P=54 is calculated. Introducing shape anisotropy lifts the cavity mode degeneracy, yielding blue- and redshifted longitudinal and transverse resonant modes, respectively. The relatively large volume over which the field enhancement is observed in these spherical and anisotropic metal shell cavities, combined with cavity quality factors that are much higher than that of the collective plasmonic modes, makes them attractive for application in nanoscale light sources, sensors, or lasers.


Item Type:Article
ORCID:
AuthorORCID
Atwater, H. A.0000-0001-9435-0201
Additional Information:© 2008 American Institute of Physics. Received 7 January 2008; accepted 3 April 2008; published 18 June 2008. Femius Koenderink (FOM-AMOLF) and Sébastien Bidault (FOM-AMOLF) are acknowledged for stimulating and helpful discussions. This work is part of the research program of the “Stichting voor Fundamenteel Onderzoek der Materie (FOM),” which is financially supported by the “Nederlandse organisatie voor Wetenschappelijk Onderzoek (NWO).”
Funders:
Funding AgencyGrant Number
Stichting voor Fundamenteel Onderzoek der Materie (FOM)UNSPECIFIED
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)UNSPECIFIED
Subject Keywords:colloids, electromagnetic wave scattering, finite difference time-domain analysis, gold, Q-factor, red shift, shells (structures), silicon compounds, surface plasmon resonance
Issue or Number:12
Record Number:CaltechAUTHORS:PENjap08
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:PENjap08
Alternative URL:http://dx.doi.org/10.1063/1.2939249
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10955
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:20 Jun 2008
Last Modified:28 Sep 2017 21:24

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