Flat Engineered Multi-Channel Reflectors

TL;DR

This paper introduces multi-channel flat reflectors using engineered metasurfaces, capable of controlling multiple propagation directions simultaneously, with experimental demonstrations of retro-reflectors and power splitters, and forecasts of future multi-functional devices.

Contribution

The paper presents a novel concept of multi-channel flat reflectors based on gradient metasurfaces, expanding light manipulation capabilities beyond single-direction control.

Findings

Designed and experimentally tested three- and five-channel retro-reflectors.

Demonstrated a three-channel power splitter.

Forecasted future multi-functional flat devices using higher-order Floquet harmonics.

Abstract

Recent advances in engineered gradient metasurfaces have enabled unprecedented opportunities for light manipulation using optically thin sheets, such as anomalous refraction, reflection, or focusing of an incident beam. Here we introduce a concept of multi-channel functional metasurfaces, which are able to control incoming and outgoing waves in a number of propagation directions simultaneously. In particular, we reveal a possibility to engineer multi-channel reflectors. Under the assumption of reciprocity and energy conservation, we find that there exist three basic functionalities of such reflectors: Specular, anomalous, and retro reflections. Multi-channel response of a general flat reflector can be described by a combination of these functionalities. To demonstrate the potential of the introduced concept, we design and experimentally test three different multi-channel reflectors: Three- and five-channel retro-reflectors and a three-channel power splitter. Furthermore, by extending the concept to reflectors supporting higher-order Floquet harmonics, we forecast the emergence of other multiple-channel flat devices, such as isolating mirrors, complex splitters, and multi-functional gratings.