Browsing by Author "Zhang, Zhengjun"

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    Near-field mapping of three-dimensional surface charge poles for hybridized plasmon modes
    (AIP Publishing LLC, 2015) Huang, Yu; Ringe, Emilie; Hou, Mengjing; Ma, Lingwei; Zhang, Zhengjun; Laboratory for Nanophotonics
    We describe a new computational approach to mapping three-dimensional (3D) surface charge poles and thus to determine complicated and hybridized plasmon modes in metallic nanostructures via finite element method (FEM) calculations. 3D surface charge distributions at the near-field resonance energies are calculated directly using Gaussﾒ law. For a nanosphere dimer, we demonstrate that higher-order hybridized plasmon modes can be addressed clearly. As an improvement to conventional mapping approaches, this new approach provides a better understanding of comprehensive physical image of plasmonic systems necessary for fundamental studies and spectroscopy applications.
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    Tunable Lattice Coupling of Multipole Plasmon Modes and Near-Field Enhancement in Closely Spaced Gold Nanorod Arrays
    (Nature Publishing Group, 2016) Huang, Yu; Zhang, Xian; Ringe, Emilie; Hou, Mengjing; Ma, Lingwei; Zhang, Zhengjun
    Considering the nanogap and lattice effects, there is an attractive structure in plasmonics: closely spaced metallic nanoarrays. In this work, we demonstrate experimentally and theoretically the lattice coupling of multipole plasmon modes for closely spaced gold nanorod arrays, offering a new insight into the higher order cavity modes coupled with each other in the lattice. The resonances can be greatly tuned by changes in inter-rod gaps and nanorod heights while the influence of the nanorod diameter is relatively insignificant. Experimentally, pronounced suppressions of the reflectance are observed. Meanwhile, the near-field enhancement can be further enhanced, as demonstrated through surface enhanced Raman scattering (SERS). We then confirm the correlation between the near-field and far-field plasmonic responses, which is significantly important for maximizing the near-field enhancement at a specific excitation wavelength. This lattice coupling of multipole plasmon modes is of broad interest not only for SERS but also for other plasmonic applications, such as subwavelength imaging or metamaterials.