Electromagnetic eigenmodes in a stacked complementary plasmonic crystal slab

Electromagnetic eigenmodes in a stacked complementary plasmonic crystal slab have been experimentally detected at optical frequencies and numerically investigated in the dispersions and the resonant field distributions. In the stacked structure, local plasmonic resonances take place as combined modes of enhanced local electric and magnetic fields, and are strongly radiative. On the other hand the plasmonic resonances, which originate from surface-plasmon polaritons and are reduced inside the light cone due to the periodic structure, appear as dispersive modes and form less confined electromagnetic field distributions. It was moreover shown that one of the reduced plasmons suppresses radiative loss and has a large quality factor as a plasmonic mode.