Classical Analog of Electromagnetically Induced Absorption in Plasmonics

The ability to manipulate the phase shift between two resonantly coupled plasmonic oscillators in a controlled fashion has been unavailable up to now. Here we present a strategy to overcome this limitation by employing the benefits of near-field coupling on the one hand and retardation effects due to far-field coupling on the other hand. We theoretically and experimentally demonstrate that in the intermediate regime the coupling of a broad dipolar to a narrow dark quadrupolar plasmon resonance is possible while simultaneously allowing for a retardation-induced phase shift. This leads to constructive interference and enhanced absorption. The observed phenomenon can thus be termed a classical analog of electromagnetically induced absorption.