  We demonstrate that the emission of light by fluorescent molecules in the
proximity of periodic arrays of nanoantennas or plasmonic crystals can be
strongly modified when the arrays are covered by a dielectric film. The
coupling between localized surface plasmon resonances and photonic states leads
to surface modes which increase the density of optical states and improve light
extraction. Excited dye molecules preferentially decay radiatively into these
modes, exhibiting an enhanced and directional emission.
