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Nanotechnology and future technological evolutions
Published in Kléber Ghimire, Future Courses of Human Societies, 2018
Notably, a new class of materials is being realized: the so-called metamaterials. In these new materials, light can bend in completely different manners compared with standard materials. In particular, light can express a negative refractive index (a value that represents the velocity of light in a medium). If this index becomes negative, it means that light in certain conditions is reflected back, instead of going forward. As Cornelia Denz et al. state in “Nonlinearities in Periodic Structures and Metamaterials”: Recent experimental demonstrations of optical metamaterials opened up an entirely new branch of optics that can be described as refractive index engineering. The refractive index is the factor by which a wave is slowed down, compared with a vacuum, when it propagates inside the material. […] One unique potential application, enabled by metamaterials is the possibility of designing a cloak of invisibility.(Denz, Flach and Kivshar, 2010, pp. 217–218)Despite the fact that the concept of invisibility was associated for a long time with myths and science fiction, the theory of metamaterials introduces the practical possibility of the development of invisibility cloaks in the future. Light can be bent around objects in such a way that the object appears totally invisible to an observer. Let us imagine a round object located in the middle of a room, with a source of light placed on its left and an observer at its right. If scientists could force each ray of light from the left to go around the curvy surface of this object and rejoin at the other side, an observer on the right side of the room would see the left side of the room unchanged, as if the object did not exist.
Photonic Technology: Recent Developments and Challenges of the Twenty-First Century
Published in Azzedine Boudrioua, Roshdi Rashed, Vasudevan Lakshminarayanan, Light-Based Science: Technology and Sustainable Development, 2017
Another class of materials that will be at the heart of technological revolution is Metamaterials [12]. These are artificial materials with physical properties ‘superior’ to natural materials. Their properties differ completely from what can be observed in natural materials. More precisely, in the fields of optics and electromagnetism, they exhibit new properties, such as a negative refractive index or an inverted Doppler effect, etc. These structures have some similarities with photonic crystals (PC), already studied for their electromagnetic properties, making it possible to control the propagation of light by photonic bandgap. These PC are rather made up of dielectrics, whereas Metamaterials use metals. Among the fields of research related to Metamaterials are invisibility, super lenses and also plasmonics. This latter is based on the fact that metals exhibit negative permittivity at optical wavelengths related to the resonance of conduction electrons (plasmons). For this reason, it is possible to make resonant structures with dimensions that are much smaller than the wavelength. Negative refraction was demonstrated for the first time by Victor Veselago in 1968, [13] indicating that the optical ray refracted by such material is on the same side of the normal as the incident ray. This amazing property paves the way for an entirely new perspective. Sir John Pendry [14] also showed that these materials with a negative refractive index make it possible to design new optical devices such as a ‘superlens’ with a theoretically perfect resolution. However, the most fascinating idea of using Metamaterials concerns very likely the invisibility. It is thought that, in the near future, a cloak of invisibility can be achieved by forcing light to bypass an object [15].
Propagation of terahertz wave in left-handed materials and the radar cross section of targets coated with left-handed materials
Published in Waves in Random and Complex Media, 2021
Gen-Ming Lai, Yu-Xin Wang, Song Liu, Shuang-Ying Zhong
In recent years, many new stealth weapons and new stealth mechanisms have emerged in the modern warfare centered on information technology. The development of left-handed materials stealth technology is a typical example. In 1968, Veselago predicated a kind of composited material named left-handed materials (LHMs), of which the permittivity ϵ and the permeability µ are both negative in a certain frequency band [1]. In 2000, Pendry et al. proposed that materials with an array of split ring resonators (SRRs) produced negative permeability over some frequency bands [2]. In 2000, Smith et al. demonstrated that the material with negative permittivity and negative permeability in microwave band was first fabricated by using copper-based composites and proved to be the existence of left-handed materials [3]. In 2006, scientists in Britain and the United States have successfully achieved the function of a ‘cloak of invisibility’ by using Gradient metamaterials obtained by similar design methods to left-handed materials [4,5]. More and more countries are trying to study the stealth technology of left-handed materials and apply them to national defense.
Editorial: an Australian perspective on multidisciplinary engineering
Published in Australian Journal of Multi-Disciplinary Engineering, 2018
In general, the undersea domain is poorly understood and underappreciated. Impervious to all radio-frequency energy except at very low frequencies, this provides a cloak of invisibility from surface, airborne and space-borne observation. Only acoustic transmissions are sufficiently far-reaching and reliable in the underwater environment to provide for communications and surveillance observation at useful ranges.