Photon harvesting by evanescent waves outgoing from very narrow grooves
Résumé
We investigate the mechanisms involved in the focusing of the optical energy in very narrow metallic grooves. This focusing drives the total absorption of a gold surface structured on a tiny part of its area (less than 3%). The key phenomenon is unveiled thanks to the decomposition of the electromagnetic field into its propagative and evanescent parts. We unambiguously show that the focusing is not due to plasmonic waves flowing toward the grooves, but rather to the magneto-electric interference of the incident wave with the evanescent field, this field being mainly due to the resonant wave escaping from the groove.
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