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Material Superabsorbs Light

Photonics.com
Jun 2008
CHESTNUT HILL, Mass., June 3, 2008 -- A metamaterial has been engineered that is capable of absorbing essentially all of the light that hits it.

Using standard optical lithography techniques, a team from Boston College in Chestnut Hill and Duke University in Durham, N.C., designed and engineered a metamaterial that uses tiny geometric surface features to successfully capture the electric and magnetic properties of a microwave to the point of total absorption, according to scientific standards.metamaterial.jpg
Boston College and Duke University researchers have engineered a metamaterial that uses tiny geometric surface features to successfully capture the electric and magnetic properties of a microwave to the point of total absorption. (Image courtesy Boston College)
Metamaterial designs give them new properties beyond the limits of their actual physical components and allow them to produce "tailored" responses to radiation. Because their construction makes them geometrically scalable, metamaterials are able to operate across a significant portion of the electromagnetic spectrum.

Because some of these man-made materials can negatively refract light, electromagnetic metamaterials are being explored by researchers as foundations for cloaking devices (See also: 'Invisible' Objects Closer and Theoretical Blueprint for Invisibility Cloak Reported).

"Three things can happen to light when it hits a material," said Boston College physicist Willie J. Padilla. "It can be reflected, as in a mirror. It can be transmitted, as with window glass. Or it can be absorbed and turned into heat. This metamaterial has been engineered to ensure that all light is neither reflected nor transmitted, but is turned completely into heat and absorbed. It shows we can design a metamaterial so that at a specific frequency it can absorb all of the photons that fall onto its surface."

In addition to Padilla, the team included BC researcher Nathan I. Landy, Duke professor David R. Smith and researchers Soji Sajuyigbe and Jack J. Mock.

The group used computer simulations based on prior research findings in the field to design resonators able to couple individually to electric and magnetic fields to successfully absorb all incident radiation, according to their findings.

Because its elements can separately absorb the electric and magnetic components of an electromagnetic wave, the "perfect metamaterial absorber" created by the researchers can be highly absorptive over a narrow frequency range and could potentially be used in devices such as bolometers (a thermometric instrument used to detect and measure radiant energy).

The metamaterial is the first to demonstrate perfect absorption and unlike conventional absorbers it is constructed solely out of metallic elements, giving the material greater flexibility for applications related to the collection and detection of light, such as imaging, said Padilla, an assistant professor of physics.

The team reported their findings in the May 23 edition of Physical Review Letters.

For more information, visit: www.bc.edu


GLOSSARY
absorption
The transfer of energy from an incident electromagnetic energy field with wavelength or frequency to an atomic or molecular medium.
glass
A noncrystalline, inorganic mixture of various metallic oxides fused by heating with glassifiers such as silica, or boric or phosphoric oxides. Common window or bottle glass is a mixture of soda, lime and sand, melted and cast, rolled or blown to shape. Most glasses are transparent in the visible spectrum and up to about 2.5 µm in the infrared, but some are opaque such as natural obsidian; these are, nevertheless, useful as mirror blanks. Traces of some elements such as cobalt, copper and...
light
Electromagnetic radiation detectable by the eye, ranging in wavelength from about 400 to 750 nm. In photonic applications light can be considered to cover the nonvisible portion of the spectrum which includes the ultraviolet and the infrared.
metamaterial
A material engineered from artificial matter not found in nature. The artificial makeup and design of metamaterials give them intrinsic properties not common to conventional materials that are exploited as light waves and sound waves interact with them. One of the most active areas of research involving metamaterials currently explores materials with a negative refractive index. In optics, these negative refractive index materials show promise in the fabrication of lenses that can achieve...
photon
A quantum of electromagnetic energy of a single mode; i.e., a single wavelength, direction and polarization. As a unit of energy, each photon equals hn, h being Planck's constant and n, the frequency of the propagating electromagnetic wave. The momentum of the photon in the direction of propagation is hn/c, c being the speed of light.
photonics
The technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. The science includes light emission, transmission, deflection, amplification and detection by optical components and instruments, lasers and other light sources, fiber optics, electro-optical instrumentation, related hardware and electronics, and sophisticated systems. The range of applications of photonics extends from energy generation to detection to communications and...
radiation
The emission and/or propagation of energy through space or through a medium in the form of either waves or corpuscular emission.
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