Artificial dielectrics are fabricated composite materials, often consisting of arrays of conductive shapes or particles in a nonconductive support matrix, designed to have specific

electromagnetic In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of a ...

properties similar to

dielectric In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the mate ...

s. As long as the lattice spacing is smaller than a

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...

, these substances can

refract In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomeno ...

and

diffract Diffraction is defined as the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a s ...

electromagnetic wave In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visib ...

s, and are used to make

lens A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...

es,

diffraction grating In optics, a diffraction grating is an optical component with a periodic structure that diffracts light into several beams travelling in different directions (i.e., different diffraction angles). The emerging coloration is a form of structura ...

s, mirrors, and

polarizer A polarizer or polariser is an optical filter that lets light waves of a specific polarization pass through while blocking light waves of other polarizations. It can filter a beam of light of undefined or mixed polarization into a beam of well ...

s for

microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ran ...

s. These were first conceptualized, constructed and deployed for interaction in the

frequency range in the 1940s and 1950s. The constructed medium, the artificial dielectric, has an effective

permittivity In electromagnetism, the absolute permittivity, often simply called permittivity and denoted by the Greek letter ''ε'' ( epsilon), is a measure of the electric polarizability of a dielectric. A material with high permittivity polarizes more in ...

and effective permeability, as intended. First published in 2004 according to the
CRC Press web page
for this book. According to the copyright page of this book, accessible via Google Books, it had gone into its tenth printing by sometime in 2005. In addition, some artificial dielectrics may consist of irregular lattices, random mixtures, or a non-uniform concentration of particles. Artificial dielectrics came into use with the radar microwave technologies developed between the 1940s and 1970s. The term "artificial dielectrics" came into use because these are

macroscopic The macroscopic scale is the length scale on which objects or phenomena are large enough to be visible with the naked eye, without magnifying optical instruments. It is the opposite of microscopic. Overview When applied to physical phenomena an ...

analogues of naturally occurring

dielectrics In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the mater ...

. The difference between the natural and artificial substance is that the atoms or molecules are artificially (human) constructed materials. Artificial dielectrics were proposed because of the need for lightweight structures and components for various microwave delivery devices. Artificial dielectrics are a direct historical link to

metamaterials A metamaterial (from the Ancient Greek, Greek word Meta, μετά ''meta'', meaning "beyond" or "after", and the Latin word ''materia'', meaning "matter" or "material") is any material engineered to have a property that is not found in naturally ...

Seminal work

The term artificial dielectric was originated by

Winston E. Kock Winston Edward Kock (1909 – November 25, 1982) was an American electrical engineer and musician, who was the first Director of NASA Electronics Research Center (NASA ERC) in Cambridge, Massachusetts, from September 1, 1964 to October 1, 1966. The ...

in 1948 when he was employed by Bell Laboratories. It described materials of practical dimensions that imitated the electromagnetic response of natural dielectric solids. The artificial dielectrics were borne out of a need for lightweight low loss materials for large and otherwise heavy devices.

Dielectric analog

Natural dielectrics, or natural materials, are a model for artificial dielectrics. When an electromagnetic field is applied to a natural dielectric, local responses and

scattering Scattering is a term used in physics to describe a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including ...

occur on the atomic or molecular level. The macroscopic response of the material is then described as

electric permittivity In electromagnetism, the absolute permittivity, often simply called permittivity and denoted by the Greek letter ''ε'' ( epsilon), is a measure of the electric polarizability of a dielectric. A material with high permittivity polarizes more in ...

and

magnetic permeability In electromagnetism, permeability is the measure of magnetization that a material obtains in response to an applied magnetic field. Permeability is typically represented by the (italicized) Greek letter ''μ''. The term was coined by William ...

. However, for this macroscopic response to be valid, a type of spatial ordering must be present between the scatterers. In addition, a certain relation to the

is part of its description. A lattice structure, with some degree of spatial ordering is present. Also, the applied field is longer in wavelength than the lattice spacing. This then allows for a macroscopic description expressed as electric permittivity and magnetic permeability. In order to manufacture an artificial permittivity and permeability there must be a capability to access the atoms themselves. This degree of precision is impractical. However, in the late 1940s - in the domain of long wavelengths such as radio frequencies and microwave - it became possible to manufacture larger scale, and more accessible scatterers that mimic the local response of natural materials - along with a synthesized

response. In the radio frequency and microwave regions such artificial crystal lattice structures were assembled. The scatterers responded to an electromagnetic field like atoms and molecules in natural materials, and the media behaved much like dielectrics with an effective media response. The scattering elements are designed to scatter the electromagnetic field in a prescribed manner. The geometric shape of the elements – spheres, disks, conducting strips, etc. – contribute to the design parameters. Copyright held by the

Institute of Electrical Engineers The Institution of Electrical Engineers (IEE) was a British professional organisation of electronics, electrical, manufacturing, and Information Technology professionals, especially electrical engineers. It began in 1871 as the Society of Tel ...

Rodded medium

The rodded medium (plasma medium) is also known as the wire mesh, and wire grid. It is a square lattice of thin parallel wires The initial research pertaining to this medium was conducted by J. Brown, K.E. Golden, and W. Rotman.Initial research on rodded medium. * Brown, J.;
Artificial dielectrics having refractive indices less than unity
; Proceedings of the IEE - Part IV: Institution Monographs Volume: 100 , Issue: 5; Publication Year: 1953 , Page(s): 51 - 62 * *

Metamaterials

Artificial dielectrics are a direct historical link to

References

{{Reflist

External links

An Artificial Dielectric
(video lecture). Electromagnetics and Applications (Physics).

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the ...

(MIT) Metamaterials Microwave technology Radio frequency propagation