  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.
