Negative Refraction with High Transmission in Graphene-hBN Hyper Crystal

TL;DR

This paper theoretically demonstrates that graphene-hBN hyper crystals can achieve all-angle negative refraction with high transmission, overcoming the low transmission issue of bare hBN, and validates the findings through simulations and effective medium theory.

Contribution

It introduces a novel hyper crystal combining graphene and hBN that exhibits all-angle negative refraction with high transmission, supported by theoretical and simulation validation.

Findings

Hyper crystal exhibits all-angle negative refraction.

High transmission achieved due to reflection suppression.

Validated by transfer matrix method and full wave simulation.

Abstract

In this article, we have theoretically investigated the performance of graphene-hexagonal Boron Nitride hyper crystals to demonstrate all angle negative refraction.Hexagonal Boron Nitride, the latest natural hyperbolic material; can be a very strong contender to form a hyper crystal with graphene due to its excellence as a graphene-compatible substrate. Although bare hexagonal Boron Nitride can exhibit negative refraction, the transmission is generally low due to its high reflective nature. On the other hand, due to two dimensional nature and metallic characteristics of graphene in the frequency range where hexagonal Boron Nitride behaves as a type-I hyperbolic Metamaterial, we have found that graphene-hexagonal Boron Nitride hyper-crystals exhibit all angle negative refraction with superior transmission. This has been possible because of the strong suppression of reflection from the hyper-crystal without any adverse effect on the negative refraction properties. This finding can prove very useful in applications such as superlensing, routing and imaging within a particular frequency range. We have also presented an effective medium description of the hyper crystal in the low k limit and validated the proposed theory using general transfer matrix method and also full wave simulation.