2010-06-06

An Artificial Black Hole for Microwaves

Scientists create artificial mini 'black hole'

(PhysOrg.com) -- Scientists from China have built a device that can trap and absorb microwaves coming from all directions with a 99% absorption rate - a property that makes the device simulate, to some extent, an astrophysical black hole. 


(Left) A model of the electromagnetic omnidirectional absorber, in which electromagnetic waves hitting the cylinder bend spirally in the shell region, and become trapped and absorbed by the lossy core. (Right) A photograph of the device, which is composed of 60 concentric layers of copper-coated metamaterials. Image credit: Institute of Physics.


The Institute of Physics

Scientists create artificial mini “black hole”


3 June 2010

Chinese researchers have successfully built an electromagnetic absorbing device for microwave frequencies. The device, made of a thin cylinder comprising 60 concentric rings of metamaterials, is capable of absorbing microwave radiation, and has been compared to an astrophysical black hole (which, in space, soaks up matter and light).

The research published today, Thursday, 3 June, in New Journal of Physics (co-owned by the Institute of Physics and German Physical Society), shows how the researchers utilised the special properties of metamaterials, a class of ordered composites which can distort light and other waves.


An omnidirectional electromagnetic absorber made of metamaterials

Author
Qiang Cheng , Tie Jun Cui 1, Wei Xiang Jiang and Ben Geng Cai

GENERAL SCIENTIFIC SUMMARY

Introduction and background. An omnidirectional perfect electromagnetic absorber may have many applications in science and engineering, such as cross-talk reduction in optoelectronic devices or solar light harvesting. However, in reality, few of the actual materials come close to 100 per cent absorption of electromagnetic waves from all directions. It is possible to reach near total absorption based on existing methods, but this is generally limited to a specific range of incidence angles.

Main results. In this work, we realize an omnidirectional electromagnetic absorber for the first time in the microwave frequencies, based on a previous theoretical work using non-magnetic metamaterials. We designed and fabricated the omnidirectional absorbing device using non-resonant metamaterials in the external layer and resonant metamaterials in the internal core, and measured the electric-field distributions using the planar-waveguide near-field scanning apparatus. Experimental results show good agreement with full-wave numerical simulations. Numerical results show that the absorption rate can reach 99 per cent in the microwave frequency.

Wider implications. The designed omnidirectional absorbing device can trap and absorb electromagnetic waves coming from all directions spirally inwards without any reflections due to the local control of electromagnetic fields. Hence it behaves like an 'electromagnetic black body' or an 'electromagnetic black hole' to some extent. Since the lossy core of the device can transfer the electromagnetic energies into heat energies, it is expected that the omnidirectional absorber could find important applications in thermal emitting and electromagnetic-wave harvesting. The more important message is that artificial metamaterials will prove remarkably more helpful and more useful for modern science and engineering.

Figure. The simulation results for a perfect omnidirectional electromagnetic absorber.



Metamaterial

Metamaterials are artificial materials engineered to provide properties which may not be readily available in nature. These materials usually gain their properties from structure rather than composition, using the inclusion of small inhomogeneities to enact effective macroscopic behavior.

The primary research in metamaterials investigates materials with negative refractive index Negative refractive index materials appear to permit the creation of superlenses which can have a spatial resolution below that of the wavelength. In other work, a form of 'invisibility' has been demonstrated at least over a narrow wave band with gradient-index materials. Although the first metamaterials were electromagnetic acoustic and seismic metamaterials are also areas of active research.


Sources
Scientists create artificial mini 'black hole'
http://www.physorg.com/news194788240.html
Scientists create artificial mini “black hole”
http://www.iop.org/News/news_41415.html
An omnidirectional electromagnetic absorber made of metamaterials
http://iopscience.iop.org/1367-2630/12/6/063006
Metamaterial - Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/Meta_materials

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