The influence of strongly focused radiation on the electromagnetic interaction of metal particles is studied. The near-field distribution of silver dimers is calculated by combining a multiple scattering approach and the multipolar expansion of focused beams based on the Richards-Wolf description of diffracting systems. The results show that tight focusing can induce larger maximum field enhancement and stronger localization of the near field than can plane wave illumination. Additional plasmonic resonances can be obtained due to the presence of different polarization contributions at focus.
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