Perfect anomalous reflectors at optical frequencies

TL;DR

This paper introduces a novel all-dielectric meta-structure that achieves near-perfect anomalous reflection at optical frequencies, overcoming previous efficiency limitations through complex wave coupling and multilayer design.

Contribution

It presents a new multilayer dielectric meta-structure capable of perfect anomalous reflection at optical frequencies, with experimental validation of high efficiency.

Findings

Achieved >99% theoretical efficiency for anomalous reflection

Demonstrated >88% experimental efficiency in fabricated devices

Enabled precise control of light direction at optical frequencies

Abstract

Reflecting light to a pre-determined non-specular direction is an important ability of metasurfaces, which is the basis for a wide range of applications (e.g., beam steering/splitting and imaging). However, anomalous reflection with 100% efficiency has not been achieved at optical frequencies in conventional metasurfaces, due to losses and/or insufficient nonlocal control of light waves. Here, we propose a new type of all-dielectric quasi-three-dimensional subwavelength structures, consisting of multilayer films and specifically designed meta-gratings, to achieve perfect anomalous reflections at optical frequencies. A complex multiple scattering process was stimulated by effectively coupling different Bloch waves and propagating waves in the proposed meta-system, thus offering the whole meta-system the desired nonlocal control on light waves required to achieve perfect anomalous reflections. Two perfect anomalous reflectors were designed to reflect normally incident 1550 nm light to the 40{\deg} and 75{\deg} directions with absolute efficiencies higher than 99%, and were subsequently fabricated and experimentally demonstrated to exhibit efficiencies 98% and 88%, respectively. Our results pave the way towards realizing optical meta-devices with desired high efficiencies in realistic applications.