Enhanced transmission and beaming via a zero-index photonic crystal

Certain types of photonic crystals with Dirac cones at the Γ point of their band structure have a zero effective index of refraction at Dirac cone frequency. Here, by an appropriate design of the photonic structure, we obtain a strong coupling between modes around the Dirac cone frequency of an all-dielectric zero-index photonic crystal and the guided ones supported by a photonic crystal waveguide. Consequently, we experimentally demonstrate that the presence of the zero-index photonic crystal at the inner side of the photonic crystal waveguide leads to an enhancement in the transmission of some of the guided waves passing through this hybrid system. Moreover, those electromagnetic waves extracted from the structure with enhanced transmission exhibit high directional beaming due to the presence of the zero-index photonic crystal at the outer side of the photonic crystal waveguide.