Direct evidence for surface plasmon-mediated enhanced light transmission through metallic nanohole arrays

This paper provides direct evidence for the role of surface plasmons in the enhanced optical transmission of light through metallic nanoscale hole arrays. Near-field optical images directly confirmed the presence of surface plasmons on gold nanohole arrays with interhole spacings larger than the surface plasmon wavelength. A simple interference model provides an intuitive explanation of the two types of fringe wavelengths observed in the near-field optical images. Far-field spectroscopy revealed a surface plasmon band that contributed a factor > 8 to the transmission enhancement. Furthermore, silicon nanohole arrays did not exhibit any features in the near-field, which demonstrates that metallic materials are necessary for enhanced light transmission through nanohole arrays.