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Oscillatory Behavior of the Long-Range Response of Localized Surface Plasmon Resonance Transducers

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posted on 27.12.2012 by Ofer Kedem, Takumi Sannomiya, Alexander Vaskevich, Israel Rubinstein
Localized surface plasmon resonance (LSPR) entails the resonance of light with collective charge density oscillations in nanostructured metal. The resonance wavelength and intensity are influenced by the nanostructures’ immediate environment as a result of the evanescently decaying plasmon electric field, which extends into the medium. Recent works on such systems have reported an oscillatory response of the LSPR peak wavelength and intensity at large nanostructure/adlayer separations well outside the accepted decay length of the evanescent field. This response was attributed to reflected fields, and a model based on image dipole interactions was proposed. In the present work we investigate in detail the interaction between plasmonic arrays and dielectric overlayers using both experiment and simulation. The oscillatory behavior is attributed to interference effects that modulate the energy distribution between the transmittance, reflectance, and absorbance channels. The observations are accurately modeled using analytical functions based on an asymmetric etalon. This treatment allowed us to separately extract the reflectivity phase and amplitude of the particle layer at all measured wavelengths by two-dimensional analysis of the extensive acquired data. The complex quantitative data, with emphasis on phase information, provide better understanding of the interaction of light with layered plasmonic structures.

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