Quasi-Two-Dimensional Hyperbolic Metamaterial for Mid-Infrared Wave Multiple Collimations

Electromagnetic (EM) wave collimation and energy harvesting are key technologies to usher a new epoch of EM applications. In this paper, a novel structure for mid-infrared wave collimation has been proposed in the scope of hyperbolic metamaterials (HMM), i.e., designing a k-space diagram as hyperbolic dispersion. The proposed HMM is a thin slab of quasi-two-dimensional (2-D) structure and is composed of alternately arranged dielectric and graphene multilayers. The quasi-2-D structure has a triangle shape on the xy-plane. Compared to the traditional metal-dielectric multilayer model, this research use graphene as replacement of the metal for mid-infrared wave collimation, which the losses are relatively low and the permittivity can be tuned through applying voltage gating. In addition, the field distribution diagrams and power density charts explicitly illustrate the performance of wave collimation. Theory and physical mechanisms of the proposed design are discussed. Research also found that the proposed structure can be utilized to generate multiple beams, and the ultimate collimations direction can be regulated.