Additional enhancement in surface-enhanced Raman scattering due to excitation geometry

Author(s)

Rosa, Lorenzo; Jayawardhana, Sasani; Juodkazis, Saulius; Stoddart, Paul R.

Available versions

Abstract

It is well known that surface-enhanced Raman scattering (SERS) substrates based on metal island films exhibit higher levels of enhancement when excited through a transparent base material than when excited directly through air. However, to our knowledge, the origin of this enhancement has never been satisfactorily explained. An initial suggestion that the additional enhancement was due to a 'nearest layer effect' cannot account for the observation of additional enhancement for monolayer adsorbates. In this paper, finite difference time domain (FDTD) modelling is presented to show that the electric field intensity in between metal particles at the interface is higher for 'far-side' excitation. This is reasonably consistent with the observed enhancement for silver islands on SiO2. The modelling results are in agreement with a simple physical model based on Fresnel reflection at the interface. This suggests that the additional enhancement is due to a near-field enhancement of the electric field due to the phase shift at the dielectric interface, when the light passes from the higher to the lower region of refractive index.

Publication year

2012

Publication type

Conference paper

Source

3rd Asia Pacific Optical Sensors Conference, Sydney, New South Wales, Australia, 31 January-03 February 2012 / John Canning and Gang-Ding Peng (eds.), Vol. 8351, paper no. 83511T

Publisher

SPIE

ISBN

9780819490278

Copyright

Copyright © 2012 Society of Photo-Optical Instrumentation Engineers. This paper was originally published in Proceedings of SPIE (Vol. 8351), and is available from: http://dx.doi.org/10.1117/12.915963. The published version is reproduced in accordance with the copyright policy of the publisher. One print or electronic copy may be made for personal use only. Systematic electronic or print reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content are prohibited.

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