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Individual gold dimers investigated by far‐ and near‐field imaging
Author(s) -
LEREU A. L.,
SANCHEZMOSTEIRO G.,
GHENUCHE P.,
QUIDANT R.,
VAN HULST N. F.
Publication year - 2008
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.2008.01895.x
Subject(s) - near and far field , plasmon , dimer , materials science , microscopy , molecular physics , near field scanning optical microscope , optical microscope , spectroscopy , nanolithography , scattering , optics , near field optics , local field , light scattering , dark field microscopy , optoelectronics , chemistry , physics , fabrication , condensed matter physics , nuclear magnetic resonance , scanning electron microscope , medicine , alternative medicine , quantum mechanics , pathology
Summary Plasmon resonances in 3D nanoparticle arrangements can produce strong localized optical fields, which are of importance for any application involving interaction of light with subwavelength volumes of matter down to the molecular level. In particular, remarkable field enhancement and confinement occur in a dimer geometry formed by two identical closely spaced particles. Although, recent advances in nanofabrication have rendered the fabrication of complex plasmon architectures more accessible, addressing their local fields in a nonperturbative fashion remains not straightforward, because metallic nanostructures are rather sensitive to their local environment. Here we study gold dimers fabricated by e‐beam lithography. Individual dimers are imaged both by far‐ and near‐field methods. First, the near‐field electromagnetic interaction in an ensemble of dimers is investigated by scattering spectroscopy, using dark field microscopy. Next, to probe their local field, we explore the luminescence of individual gold dimers utilizing a confocal microscope with single molecule detection sensitivity. We provide a statistical analysis of the dimer luminescence for different incident polarizations, with direct comparison to single particles (monomers). Finally, the near‐field transmission of the resonant dimers is mapped with a subwavelength resolution using polarized controlled near‐field scanning optical microscopy. Surprisingly, no clear evidence of the high mode density in the dimer gap is observed. This result may be attributed to the limited coupling of the field emitted by the aperture probe to the dimer mode.