Showing posts with label Metamaterials. Show all posts

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.

Collected from: Scientists create artificial mini 'black hole'

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.

Collected from: Scientists create artificial mini “black hole”

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.

Collected from: An omnidirectional electromagnetic absorber made of metamaterials

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.

Collected from: Metamaterial - Wikipedia, the free encyclopedia

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

Scientists create artificial mini 'black hole'
http://www.sciencedaily.com/releases/2010/06/100603091829.htm
Scientists create artificial mini 'black hole'
http://www.physorg.com/news194788240.html
1367-2630_12_6_063006.pdf - Powered by Google Docs
http://docs.google.com/viewer?url=http://iopscience.iop.org/1367-2630/12/6/063006/pdf/1367-2630_12_6_063006.pdf
How to Create a Black Hole on a Lab Bench | 80beats | Discover Magazine
http://blogs.discovermagazine.com/80beats/2009/10/14/how-to-create-a-black-hole-on-a-lab-bench/
Researchers Create an Electromagnetic "Black Hole" the Size of a Salad Plate: Scientific American
http://www.scientificamerican.com/article.cfm?id=electromagnetic-black-hole
Scientists Make Desktop Black Hole | Wired Science | Wired.com
http://www.wired.com/wiredscience/2009/10/desktop-black-hole/
First black hole for light created on Earth - physics-math - 14 October 2009 - New Scientist
http://www.newscientist.com/article/dn17980-first-black-hole-for-light-created-on-earth.html
Technology Review: Blogs: arXiv blog: Artificial Black Hole Created in Chinese Lab
http://www.technologyreview.com/blog/arxiv/24234/
Scientists Create Artificial Mini 'Black Hole': An Omnidirectional Electromagnetic Absorber Made Of Metamaterials | Before It's News
http://beforeitsnews.com/news/72/578/Scientists_Create_Artificial_Mini_Black_Hole:_An_Omnidirectional_Electromagnetic_Absorber_Made_Of_Metamaterials.html

2009-11-24

Metamaterials To Develop Invisibility Cloaks

clipped from www.asylum.com

Scientists Working on Invisibility Cloak

The Imperial College of London and the University of Southampton have been awarded a £4.9 million grant from the Leverhulme Trust to further research "metamaterials" that could hopefully bend light away as it reflects from the surface, tricking the human eye into believing an item made of metamaterials is not there. To create the materials, scientists have to alter the structure of an already existing material using complex nanopatterns. In other words, eerily floating chess pieces for everyone!

clipped from www.dailymail.co.uk

We may be seeing Harry Potter's invisibility suit sooner than we think...

Fiction made real? Harry Potter goes invisible in the 'Goblet of Fire'

A photo of 'meta-material', which can deflect microwave beams so they flow around a 'hidden' object

clipped from www3.imperial.ac.uk

£4.9 million to develop metamaterials for 'invisibility cloaks' and 'perfect lenses'
Imperial receives major new funding grant from The Leverhulme Trust - News Release

The new grant is one of two The Leverhulme Trust is awarding for 'embedding emerging disciplines'. The project team is led by two of Imperial College London's Professors: Professor Sir John Pendry, a world-leading physicist and pioneer in the field, who first proposed that metamaterials could be used to build an invisibility 'cloak' in 2006, and Professor Stefan Maier who is a leading experimentalist in the field of plasmonics. Also collaborating in the project is Professor Nikolay Zheludev's team at the University of Southampton.

clipped from physics.aps.org

Taking the wraps off cloaking

$(Top) A hot desert surface causes a refractive index gradient in the air above, causing rays of light to be refracted continuously to form a reflection in the road and hence the appearance of water. (Bottom) Similarly, a graded refractive index cloak can guide light around a hidden object so that an observer sees only that which is behind the cloak.$

Illustration: Top: www.dreamstime.com; Bottom: Pendry et al. [7]

$(Top left) A ray of light in free space travels in a straight line. The undistorted coordinate system is shown. (Top right) The coordinates are transformed to exclude the cloaked region. Trajectories of rays are pinned to the coordinate mesh and therefore avoid the cloaked region, returning to their original path after traversing the cloak. (Bottom) In contrast, this cloaking scheme operates by cancelling scattering due to the hidden object. Here we show a high-refractive-index sphere hidden by$

A ray of light in free space travels in a straight line. The undistorted coordinate system is shown. (Top right) The coordinates are transformed to exclude the cloaked region. Trajectories of rays are pinned to the coordinate mesh and therefore avoid the cloaked region, returning to their original path after traversing the cloak.

$(Top left) The first implementation of a cloak: resonant elements, shown inset, are incorporated in a metamaterial and tuned to give a magnetic response graded from the inner to outer radius. Dimensions are shown in mm. The cloak is designed to operate at $8.5\ \textrm{GHz}$. (Bottom left) A proposed design for an optical version of the cloak, incorporating metal wires in a dielectric host and designed to operate at $632.8\ \textrm{nm}$ in a cloak approximately 4 microns in diameter. The latter$

Illustration: Top left: Schurig et al. [11]; bottom left: Smolyaninov et al. [21]; top and bottom right: Valentine et al. [19]

Illustration: Torrent and Sánchez-Dehesa [28]

Figure 5: (Left) Schematic view of the acoustic cloaking shell consisting of two different materials of the same thicknesses arranged in a cylindrical multilayered structure. (Right) Pressure map for a planar wave incident on a multilayer structure comprising 200 layers.

clipped from www.dailymotion.com

Sources:

New Metamaterials Promise Invisibility Cloaks

Metamaterials

Clipped from: Metamaterials Hold Promise For Invisibility Cloaks -- Metamaterials -- InformationWeek

Metamaterials Hold Promise For Invisibility Cloaks

Researchers at the University of California, Berkeley, say they have created materials that bring them closer to creating invisibility cloaks.

They will publish their work in two journals, Nature and Science, this week. The researchers used 3-D metmaterials, or composites with the ability to bend electromagnetic waves, to negatively refract light

Negative refraction

Clipped from: Professor Xiang Zhang's Research Lab - UC Berkeley: Home

Invisibility

Clipped from: Invisibility cloak a step closer as scientists bend light 'the wrong way' | Mail Online

Invisibility cloak a step closer as scientists bend light 'the wrong way'

The discoveries could one day allow people to become invisible

Research

Clipped from: Professor Xiang Zhang's Research Lab - UC Berkeley: Home

Negative Refraction New Breakthroughs! read the story

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