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A cloaking device is a hypothetical or fictional stealth technology that can cause objects, such as spaceships or individuals, to be partially or wholly invisible to parts of the electromagnetic (EM) spectrum. Fictional cloaking devices have been used as plot devices in various media for many years.
Invisibility is the state of an object that cannot be seen. An object in this state is said to be invisible. The phenomenon is studied by physics and perceptual psychology.
A metamaterial is any material engineered to have a property that is not found in naturally occurring materials. They are made from assemblies of multiple elements fashioned from composite materials such as metals and plastics. The materials are usually arranged in repeating patterns, at scales that are smaller than the wavelengths of the phenomena they influence. Metamaterials derive their properties not from the properties of the base materials, but from their newly designed structures. Their precise shape, geometry, size, orientation and arrangement gives them their smart properties capable of manipulating electromagnetic waves: by blocking, absorbing, enhancing, or bending waves, to achieve benefits that go beyond what is possible with conventional materials.
A superlens, or super lens, is a lens which uses metamaterials to go beyond the diffraction limit. For example, in 1995, Guerra combined a transparent grating having 50nm lines and spaces with a conventional microscope immersion objective. The resulting "superlens" resolved a silicon sample also having 50nm lines and spaces, far beyond the classical diffraction limit imposed by the illumination having 650nm wavelength in air. The diffraction limit is a feature of conventional lenses and microscopes that limits the fineness of their resolution depending on the illumination wavelength and the numerical aperture NA of the objective lens. Many lens designs have been proposed that go beyond the diffraction limit in some way, but constraints and obstacles face each of them.
A cloak of invisibility is a fictional theme. In folklore, mythology and fairy tales, a cloak of invisibility appears either as a magical item used by duplicitous characters or an item worn by a hero to fulfill a quest. It is a common theme in Welsh and Germanic folklore, and may originate with the cap of invisibility seen in ancient Greek myths. The motif falls under "D1361.12 magic cloak of invisibility" in the Stith Thompson motif index scheme.
A split-ring resonator (SRR) is an artificially produced structure common to metamaterials. Their purpose is to produce the desired magnetic susceptibility in various types of metamaterials up to 200 terahertz.
Negative-index metamaterial or negative-index material (NIM) is a metamaterial whose refractive index for an electromagnetic wave has a negative value over some frequency range.
A terahertz metamaterial is a class of composite metamaterials designed to interact at terahertz (THz) frequencies. The terahertz frequency range used in materials research is usually defined as 0.1 to 10 THz.
Metamaterial antennas are a class of antennas which use metamaterials to increase performance of miniaturized antenna systems. Their purpose, as with any electromagnetic antenna, is to launch energy into free space. However, this class of antenna incorporates metamaterials, which are materials engineered with novel, often microscopic, structures to produce unusual physical properties. Antenna designs incorporating metamaterials can step-up the antenna's radiated power.
An acoustic metamaterial, sonic crystal, or phononic crystal, is a material designed to control, direct, and manipulate sound waves or phonons in gases, liquids, and solids. Sound wave control is accomplished through manipulating parameters such as the bulk modulus β, density ρ, and chirality. They can be engineered to either transmit, or trap and amplify sound waves at certain frequencies. In the latter case, the material is an acoustic resonator.
A tunable metamaterial is a metamaterial with a variable response to an incident electromagnetic wave. This includes remotely controlling how an incident electromagnetic wave interacts with a metamaterial. This translates into the capability to determine whether the EM wave is transmitted, reflected, or absorbed. In general, the lattice structure of the tunable metamaterial is adjustable in real time, making it possible to reconfigure a metamaterial device during operation. It encompasses developments beyond the bandwidth limitations in left-handed materials by constructing various types of metamaterials. The ongoing research in this domain includes electromagnetic materials that are very meta which mean good and has a band gap metamaterials (EBG), also known as photonic band gap (PBG), and negative refractive index material (NIM).
A photonic metamaterial (PM), also known as an optical metamaterial, is a type of electromagnetic metamaterial, that interacts with light, covering terahertz (THz), infrared (IR) or visible wavelengths. The materials employ a periodic, cellular structure.
A nonlinear metamaterial is an artificially constructed material that can exhibit properties not found in nature. Its response to electromagnetic radiation can be characterized by its permittivity and material permeability. The product of the permittivity and permeability results in the refractive index. Unlike natural materials, nonlinear metamaterials can produce a negative refractive index. These can also produce a more pronounced nonlinear response than naturally occurring materials.
Metamaterial cloaking is the usage of metamaterials in an invisibility cloak. This is accomplished by manipulating the paths traversed by light through a novel optical material. Metamaterials direct and control the propagation and transmission of specified parts of the light spectrum and demonstrate the potential to render an object seemingly invisible. Metamaterial cloaking, based on transformation optics, describes the process of shielding something from view by controlling electromagnetic radiation. Objects in the defined location are still present, but incident waves are guided around them without being affected by the object itself.
The history of metamaterials begins with artificial dielectrics in microwave engineering as it developed just after World War II. Yet, there are seminal explorations of artificial materials for manipulating electromagnetic waves at the end of the 19th century. Hence, the history of metamaterials is essentially a history of developing certain types of manufactured materials, which interact at radio frequency, microwave, and later optical frequencies.
Transformation optics is a branch of optics which applies metamaterials to produce spatial variations, derived from coordinate transformations, which can direct chosen bandwidths of electromagnetic radiation. This can allow for the construction of new composite artificial devices, which probably could not exist without metamaterials and coordinate transformation. Computing power that became available in the late 1990s enables prescribed quantitative values for the permittivity and permeability, the constitutive parameters, which produce localized spatial variations. The aggregate value of all the constitutive parameters produces an effective value, which yields the intended or desired results.
A plasmonic metamaterial is a metamaterial that uses surface plasmons to achieve optical properties not seen in nature. Plasmons are produced from the interaction of light with metal-dielectric materials. Under specific conditions, the incident light couples with the surface plasmons to create self-sustaining, propagating electromagnetic waves known as surface plasmon polaritons (SPPs). Once launched, the SPPs ripple along the metal-dielectric interface. Compared with the incident light, the SPPs can be much shorter in wavelength.
Costas M. Soukoulis is a Senior Scientist in the Ames Laboratory and a Distinguished Professor of Physics Emeritus at Iowa State University. He received his B.Sc. from University of Athens in 1974. He obtained his Ph.D. in Physics from the University of Chicago in 1978, under the supervision of Kathryn Liebermann Levin. From 1978 to 1981 he was at the Physics Department at University of Virginia. He spent 3 years (1981–84) at Exxon Research and Engineering Co. and since 1984 has been at Iowa State University (ISU) and Ames Laboratory. He has been part-time Professor at the Department of Materials Science and Technology of the University of Crete (2001-2011) and an associated member of IESL-FORTH at Heraklion, Crete, Greece since 1984.
Illusion optics is an electromagnetic theory that can change the optical appearance of an object to be exactly like that of another virtual object, i.e. an illusion, such as turning the look of an apple into that of a banana. Invisibility is a special case of illusion optics, which turns objects into illusions of free space. The concept and numerical proof of illusion optics was proposed in 2009 based on transformation optics in the field of metamaterials. It is a scientific disproof of the idiom 'Seeing is Believing'.
Sergei Anatolyevich Tretyakov is a Russian-Finnish scientist, focused in electromagnetic field theory, complex media electromagnetics and microwave engineering. He is currently a professor at Department of Electronics and Nanoengineering, Aalto University, Finland. His main research area in recent years is metamaterials and metasurfaces from fundamentals to applications. He was the president of the European Virtual Institute for Artificial Electromagnetic Materials and Metamaterials and general chair of the Metamaterials Congresses from 2007 to 2013. He is a fellow/member of many scientific associations such as IEEE, URSI, the Electromagnetics Academy, and OSA. He is also an Honorary Doctor of Francisk Skorina Gomel State University.
References
- ↑ Shelby, R. A.; Smith, D. R.; Schultz, S. (2001), "Experimental verification of a negative index of refraction", Science, 292 (5514): 77–79, Bibcode:2001Sci...292...77S, CiteSeerX 10.1.1.119.1617 , doi:10.1126/science.1058847, JSTOR 3082888, PMID 11292865, S2CID 9321456
- ↑ Pendry, John B. (2004). "Negative Refraction" (PDF). Contemporary Physics. 45 (3): 191–202. Bibcode:2004ConPh..45..191P. doi: 10.1080/00107510410001667434 . S2CID 218544892. Archived from the original (PDF) on 2011-07-17. Retrieved 2009-08-26.
- ↑ "David R. Smith Shares Descartes Award for Material that Reverses Lights Properties". 2005-12-02. Retrieved 2009-10-16.
- ↑ Hapgood, Fred (2009-03-10). "Metamaterial Revolution: The New Science of Making Anything Disappear" . Retrieved 2009-10-10.
- 1 2 Silverman, Jacob (2007-06-25), HowStuffWorks: Is it possible to make a cloaking device? , retrieved 2009-10-16
- ↑ "Theoretical Blueprint For Invisibility Cloak Reported". 2006-05-25. Retrieved 2009-10-16.
- ↑ "Thomson Reuters Predicts Nobel Laureates". 2009-09-24. Archived from the original on 2012-09-13.
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