Direct Evidence for Surface Plasmon-Mediated Enhanced Optical Transmission through Nanohole Arrays

By combining near-field and far-field spectroscopy, we have provided direct evidence for the role of surface plasmons (SPs) 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. Either lambda (SP) or lambda (SP)/2 was observed depending upon the thickness of the film. Far-field spectroscopy revealed a surface plasmon band that contributed a factor over eight times to the transmission enhancement.