Plasmonic electromagnetically-induced transparency in symmetric structures

A broken symmetry is generally believed to be a prerequisite for plasmonic electromagnetically-induced transparency (EIT), since the asymmetry allows the excitation of the otherwise forbidden dark mode. Nevertheless, according to the picture of magnetic plasmon resonance (MPR)-mediated plasmonic EIT, we show that plasmonic EIT can be achieved even in symmetric structures, provided that we take into account the plasmonic modes beyond the fundamental ones. This not only sharpens our understanding of the existing concept, but also provides a profound insight into the plasmonic coherent interference in the near-field zone. (C) 2010 Optical Society of America