Inter-slit Coupling in Gold Film Hole Arrays
  Inter-slit interactions across one-dimensional arrays of sub-micro meter rectangular holes in gold films are explored. Using electron energy loss spectroscopy combined with scanning transmission electron microscopy, a series of cavity standing waves is resolved, indicating particularly high interslit interactions, about an order of magnitude larger than the intra-slit edge to edge coupling. Pronounced signal enhancements are thus induced, dominated by short-range interactions and high mode-localization, while yet, relatively long-range coherence is retained. The sub-nm electron beam, in spite of principal differences from broad-area probes, yields results similar to extraordinary optical transmission (EOT). Implications to EOT mechanisms, including its sub-wavelength, off-resonance limit, are pointed out. 
Itai Carmeli, Roman Walther, Reinhard Schneider, Dagmar Gerthsen,   Yaron Kaufman, Ayala Shvarzman, Shachar Richter, Hagai Cohen
physics.optics