Light funneling mechanism explained by magneto-electric interference

TL;DR

This paper explains how optical energy is funneled into sub-wavelength grooves on metal surfaces through magneto-electric interference, challenging the plasmonic wave explanation.

Contribution

It reveals that magneto-electric interference, not plasmonic waves, is responsible for energy funneling into metallic grooves.

Findings

Funneling is caused by magneto-electric interference.

Evanescent fields mainly originate from resonant waves in the grooves.

Plasmonic waves are not the primary mechanism for energy transfer.

Abstract

We investigate the mechanisms involved in the funneling of the optical energy into sub-wavelength grooves etched on a metallic surface. The key phenomenon is unveiled thanks to the decomposition of the electromagnetic field into its propagative and evanescent parts. We unambiguously show that the funneling 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.