Plasmonic and photonic nanostructures for radiative control
Light propagating in a periodic structure is described by Bloch waves, analogous to the description of electronic states in crystals. The dispersion relation for light in such structures can thus be modified by the band structure prescribed by the symmetry of the lattice and the dielectric contrast. Excitation of a surface plasmon in a metallic nanostructure allows similar control over the surface plasmon polariton, which due to the plasmon resonance, can have extremely large fields in local regions of space. Coupling of a two- or more-level electronic system to optical fields whose dispersion relation is modified by such a photonic bandstructure presents an interesting opportunity to control the light-matter interaction to suppress or enhance the radiative rate(s) of the system. We have employed these concepts to enhance the efficiency of near-infrared to visible upconversion in rare-earth doped nanocrystals. Figure 1 shows an example of this work, where we excite the surface plasmon polariton at 980nm in a nanostructured Au two dimensional crystal, and coupled these excitations to NIR to visible upconverting phosphors embedded in NaYF4 nanoparticles. In this work, we use Finite Difference Time Domain (FDTD) method as a design tool to analyze the photonic properties of the metallic nanostructures, and imaging methods to assess the upconversion efficiency.
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H.P. Paudel, L. Zhong, K. Bayat, M.F. Baroughi, S. Smith, C. Lin, C. Jiang, M.T. Berry, and P.S. May, "Enhancement of Near-Infrared-to-Visible Upconversion Luminescence Using Engineered Plasmonic Gold Surfaces," J. Phys. Chem C 115 (39) pp 1902819036 (2011).
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Peng Zhang, Steve Smith, Garry Rumbles and Michael E. Himmel, "Direct Imaging of Surface-Enhanced Raman Scattering in the Near Field," Langmuir 21 520 (2005).