Anti-reflection coatings for epsilon-near-zero materials

Epsilon-near-zero (ENZ) materials have attracted much interest within the photonics community due to the various novel light-matter interactions that can occur in the ENZ regime. These materials display a large impedance mismatch between the ENZ material and free space, making it difficult to couple light into the medium at normal incidence. In this article, we demonstrate that enhanced light coupling into an ENZ metamaterial stack can be achieved via the design and fabrication of anti-reflection coatings, which are simple to fabricate via e-beam evaporation. The coating fabricated has been optimized not only to minimize reflection but also aims to maximize transmission - making these designs applicable to e.g. beam shaping applications. We achieve a transmission enhancement of 20% through our metamaterial over a 150 nm range and reflection minimization of 50% over a 200 nm range.Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.