Accurate measurement of Rayleigh scattering is crucially important for fundamental understanding of the plasmonic properties of meltimeric (≥ 3) nanoparticles that can be served as efficient SERS sensing platforms and nanophotonic materials. Thus, using the laser-scanning assisted dark-field microscopy that enabled to precisely collect far-field (Rayleigh) scattering from the centers of individual trimeric nanoparticles, we monitored spectral redistributions of oscillating coupled plasmonic modes as a function of trimer symmetry. As a consequence of the precise measurement of the polarization-resolved Rayleigh scattering spectra obtained from triangular trimers to linear trimers via elongated triangular trimers, the in-phase horizontally oscillating plasmonic mode with the largest dipole moment is found to be greatly increased by 20-folds, whereas the axially oscillating plasmonic mode with the second-largest dipole moment is dramatically decreased by 70-folds. Consequently, the overall quantity of the far-field scattering, the total sum of the individual coupled plasmonic modes, was gradually increased by 2-folds. The precise polarization-resolved Rayleigh scattering measurement also visualizes directly the directions of the radiation fields of individual oscillating coupled plasmonic modes, which would be valuable information in systematic controlling the polarization direction of the scattered light from the trimers. Overall, we showed an exemplary quantitative and extensive study of the coupled plasmonic modes from nanoparticles, giving a simple but clear insight.
Haemi Lee, Jung-Hoon Lee, Jwa-Min Nam, and Yung Doug Suh, "Sub-one-nanometer gap (SONG) for nanogap-enhanced Raman scattering (NERS)," Proc. SPIE 9925, Nanoimaging and Nanospectroscopy IV, 99250J (Presented at SPIE Nanoscience + Engineering: August 29, 2016; Published: 27 October 2016); https://doi.org/10.1117/12.2239605.
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