Metamaterials for light rays: ray optics without wave-optical analog in the ray-optics limit

TL;DR

This paper explores the concept of METATOYs, optical sheets that manipulate light rays in novel ways, and investigates whether their ray-optical transformations have wave-optical analogs, revealing limitations in wave optics.

Contribution

It introduces METATOYs as optical metamaterials for light rays and analyzes the existence of wave-optical analogs for their transformations, highlighting limitations.

Findings

Wave-optical analogs do not always exist for METATOYs transformations.

Many ray-optical possibilities of METATOYs are unexplored due to wave-optical limitations.

The study clarifies the boundary between ray optics and wave optics for optical metamaterials.

Abstract

Volumes of sub-wavelength electromagnetic elements can act like homogeneous materials: metamaterials. In analogy, sheets of optical elements such as prisms can act ray-optically like homogeneous sheet materials. In this sense, such sheets can be considered to be metamaterials for light rays (METATOYs). METATOYs realize new and unusual transformations of the directions of transmitted light rays. We study here, in the ray-optics and scalar-wave limits, the wave-optical analog of such transformations, and we show that such an analog does not always exist. Perhaps, this is the reason why many of the ray-optical possibilities offered by METATOYs have never before been considered.