Dynamic evolution of surface plasmon resonances in metallic nanoslit arrays

Abstract

We have investigated surface plasmon interactions in a metallic nanoslit array structure that shows characteristic transmission spectra with well-defined transmission minima and maxima in the visible-to-infrared range. The time evolution of the surface plasmon resonances occurring in various different regimes of the spectra was analyzed by performing finite-difference time-domain analysis of the plasmon field, energy flow, and polarization charge distributions in the nanoslit array structure. At the transmission dip that corresponds to the surface plasmon resonance at metal/dielectric(substrate) interface, the polarization charges are found to distribute such that they form in-plane standing-wave oscillations along the dielectric side of the metal surface. At the transmission peak, surface plasmon waves oscillate along the periphery of each metal island with a quadrupolar distribution of polarization charges. At the longer wavelength regime, the polarization charges at each island show a dipolar distribution along the array direction. Optical transmission in this regime is found to critically depend on slit width, which affects the near-field coupling between metal islands.