Directional, multi-beam, and compact wavefront transformers based on 3-D near-zero refractive index metamaterial

Abstract

Optical wavefront transformation is essential for communication and power transfer applications across all electromagnetic spectra. In this work, we report directional multi-beam compact wavefront transformers which convert cylindrical wavefronts into finite-aperture directional beams based on near-zero refraction in 3-D metamaterial at terahertz frequencies. For this purpose, a near-zero-index metamaterial (NZIM) with three-dimensional functionality is realized, and its effective material parameters are retrieved. Near-zero refraction in NZIM is verified through the uniform phase maintenance inside the multiple stacked NZIM layers. By embedding a cylindrical wavefront source inside NZIM configurations, uni-, bi-, and quad-directional wavefront transformers are realized. The results were compared and verified against the ideal cases.