China
Africa
Explore chapters and articles related to this topic
Photonic Metamaterials
Published in Pankaj K. Choudhury, Metamaterials, 2021
Metamaterials, composed of sub-wavelength artificial unit cells, open up wide avenues in optical applications, such as perfect lenses [26] and invisibility cloaks [27,28]. Unusual hyperbolic dispersion curves [29–39] supporting radiative modes with unbounded wave numbers give rise to tremendous interest in hyperbolic metamaterials (HMMs). Because of the extreme anisotropy in the uniaxial permittivity tensor, HMMs give rise to unique properties. The hyperbolicity occurs when one of the diagonal tensor components is opposite in sign from the other two components. This unique material dispersion is attributed to the novel optical properties of HMMs. This includes a negative refractive index in a waveguiding geometry [40], nominally unbounded density of photonic states [41], and the existence of an ENZ (epsilon-near-zero) wavelength range for one of the permittivity components [42].
Electromagnetic characterization of strong-coupled Omega-type bianisotropic metamaterials using the state transition matrix method
Published in Waves in Random and Complex Media, 2021
Ugur Cem Hasar, Gokhan Ozturk, Mehmet Ertugul, Joaquim José Barroso, Omar M. Ramahi
Due to their extraordinary electromagnetic applications such as perfect lenses and invisibility cloaks [1, 2], engineered materials, which are typically referred to as metamaterials (MMs), have drawn enormous attention from the scientific community. To get the full benefit of these materials, their electromagnetic responses should be characterized. To meet this demand, many extraction techniques were proposed for a variety of purposes. Scattering (S-) parameter extraction techniques can be categorized into commonly used extraction procedure and new form of extraction procedure [3–25]. In the commonly used extraction procedure, the complex wave equation is solved and then the boundary conditions are enforced to evaluate the unknown terms of the solution [3–23, 25]. In the new form of the extraction procedure, which is called the state transition matrix (STM) extraction procedure, electromagnetic properties such as propagation constant and wave impedance terms are derived directly from coupled Maxwell equations without resorting to the solution of the uncoupled complex wave equations [24, 26–28].
Reflection characteristics of superconductor-dielectric-superconductor junction at near-zero permittivity region
Published in Electromagnetics, 2019
Peng Chen, Luping Li, Kai Yang
Refractive index is defined as the ratio of the light speed in vacuum and the light speed in a medium. As the medium molecules always have thermal collisions when their ambient temperature are over absolute zero, the speed of light in the medium is often less than that in vacuum, which makes the refractive index greater than 1. Veselago (1968) proposed a hypothesis that conductance and permeability can be negative. Pendry has found that both the relative conductance and permeability could be negative when a split ring resonator is used to transform the electromagnetic wave. He named this new material as metamaterial (Pendry 2006). Soon more and more scientists began to use the metamaterial for various applications, such as filter and antenna (Kokkinos, Sarris, and Eleftheriades 2006; Studniberg and Eleftheriades 2009; Zhang, Fluegel, and Mascarenhas 2003). The metamaterial can greatly reduce the size of the radiofrequency (RF)/microwave circuits. Another application of the metamaterial is to design electromagnetic invisibility cloaks (Leonhardt 2006; Pendry 2006). As a tremendous potential application in the military, the electromagnetic invisibility cloaks soon became the research hot spot.
Editor’s message: microwave processing of modern materials
Published in Journal of Microwave Power and Electromagnetic Energy, 2020
Although the term metamaterial is a way to make a distinction from other advancements in materials science and engineering, the modern reference to them considers “exotic” interaction with electromagnetic waves. Metamaterials are designed in size, shape and combination of different materials that can be stacked to form periodical arrangements, smaller than the wavelength. The list of applications is long; one that seems like science fiction is the invisibility cloak, by bending the wave propagation around an object, and that has been proven with some degree of success.