Enhanced coupling of plasmons in hole arrays with periodic dielectric antennas.

We compare the angle-dependent transmission spectra of a metal hole array with dielectric pillars in each hole with that of a conventional metal hole array. The pillars enhance the optical transmission as well as the interaction between surface plasmon modes. This results in an observed splitting Delta omega/omega as large as 6%, at normal incidence, for the modes on the pillar side of the array.