Unidirectional light transmission by two-layer nanostructures interacting via optical near-fields

TL;DR

This paper demonstrates unidirectional light transmission through two-layer nanostructures by exploiting optical near-field interactions, showing that different polarization conversion efficiencies in forward and backward directions lead to non-reciprocal light flow.

Contribution

The study provides experimental evidence of unidirectional light transmission enabled by near-field interactions in two-layer nanostructures, confirming theoretical predictions.

Findings

Unidirectional transmission observed experimentally.

Polarization conversion efficiencies differ in forward and backward directions.

Near-field interactions facilitate non-reciprocal light transfer.

Abstract

We experimentally demonstrate unidirectional light transmission through two-layer nanostructured materials considering that the horizontal-to-vertical-polarization conversion efficiency in the forward direction and the vertical-to-horizontal efficiency in the backward direction, which are usually equivalent due to optical reciprocity, are different. The different ways of transferring light momentum in the forward and backward directions via optical near-fields between the layers are responsible for the unidirectionality of light, which was theoretically investigated in our recent work [J. Opt. Soc. Am. B 31, 2404-2413]. With two-layer metal nanostructures experimentally fabricated via a repeated lift-off technique, consistent optical characteristics are observed, verifying the utilization of the large momentum of optical near-fields.