Reflectionless zero refractive index metasurface in the terahertz waveband

Abstract

Zero refractive index materials behave electromagnetically as single points despite the finite dimensions because a propagating electromagnetic wave passes with an infinite phase velocity. However, the composition of naturally occurring materials cannot produce a zero refractive index material because any effect of both of the dielectric and magnetic properties would have to vanish (be near zero). In this report, we demonstrate a zero refractive index metasurface with a refractive index of 0.16 + j0.09, the reflectance of 0.7%, and transmittance of 97.3% at 0.505 THz. The measured relative permittivity and relative permeability are 0.18 − j0.10 and 0.004 + j0.16 at 0.505 THz, respectively. Both the relative permittivity and relative permeability simultaneously approach zero at the same frequency, and the dielectric and magnetic properties appear to be absent (vanish) in the artificial material. The zero refractive index metasurface can offer a material platform for terahertz applications with unprecedented functionalities for 6G (beyond 5G) wireless communications, imaging, and security.

A Terahertz Demultiplexer Based on Metamaterials Applied to Terahertz Communication Systems

“…We can see that at 0.225 THz, the effective permittivity is 0.12−0.002j, and the permeability is 0.11+0.001j, so the effective impedance is close to 1. In the range of 0.23 THz ∼ 0.24 THz, the effective permittivity and permeability are close to zero, as shown in the shaded part, and some scholars have found that near-zero refractive index materials have the characteristics of high transmittance [18]. There are zero refractive indexes near 0.225 THz, which is the representation for the maximum transmittance of metamaterials.…”

Single-Layer, Unidirectional, Broadside-Radiating Planar Quadrupole Antenna for 5G IoT Applications

“…Consequently, our initial attempt to achieve a via-less magnetic dipole response was to simply use the magnetic dipole antenna arising from the Huygens dipole antenna design in [15], remove the EAD NFRP element, and then remove all four vias of the CLL NFRP elements. It was anticipated that this would be successful because of the vaunted first magnetic optical metamaterial based on two parallel conducting strips [20], a concept that has been extended recently to attain a matched zero refractive index metasurface in the terahertz band [21]. However, it was unsuccessful for the following reasons.…”

“…2(b) was assessed with a plane wave excitation of the equivalent two passive strip configuration, i.e., with them as scatterers. This model represents one unit cell of the infinite metasurface constructs considered in [20], [21]. Since the electric quadrupolar response was realized in the finite antenna design rather than a magnetic dipole one upon which those works were based, quadrupolar scattering results would also represent an additional contribution, i.e., one to the fundamental understanding of how finite electromagnetic metastructure designs actually work.…”

“…However, without those vertical walls/vias, the parallel strips cannot achieve the loop current needed to form a magnetic dipole. Moreover, because the number of strips is small and they are not members of the infinite optical metamaterial slab configuration excited by a "plane wave" originating from a distant source [20], [21], they do not achieve a magnetic dipole response. Rather, simple parallel strip combinations can achieve an electric quadrupole, whether they are excited by a nearby dipole or distant plane wave source, and their near-field integration with a driven dipole yields a unidirectional pattern that is not a perfect cardioid shape, but one that has a practically useful front-toback ratio (FTBR).…”

Modified Hexagonal Split Ring Resonator Based on an Epsilon-Negative Metamaterial for Triple-Band Satellite Communication

“…Contrarily, metamaterials yield both negative permittivity and negative permeability or either trait can be negative by itself. An engineered structure indicating both negative permittivity and permeability is called a double negative (DNG) metamaterial, while a structure manifesting either negative value is called a single negative (SNG) metamaterial [ 1 , 2 ]. DNG and SNG metamaterials are extensively used in different technological developments.…”