Go Back   AFA Forums > Science, Logic and Reason > General Science News

General Science News Got an idea, article or video you want to share on Science, Philosophy or Evolution?

Reply
 
Thread Tools
  #1  
Old 29th January 2012, 03:04 PM
Darwinsbulldog's Avatar
Darwinsbulldog Darwinsbulldog is offline
Science Moderator
 
Join Date: Jan 2009
Location: Perth
Posts: 11,395
Default Scientists Create First Free-Standing 3-D Cloak

Quote:
ScienceDaily (Jan. 25, 2012) Researchers in the US have, for the first time, cloaked a three-dimensional object standing in free space, bringing the much-talked-about invisibility cloak one step closer to reality.
Whilst previous studies have either been theoretical in nature or limited to the cloaking of two-dimensional objects, this study shows how ordinary objects can be cloaked in their natural environment in all directions and from all of an observer's positions.
Published Jan. 26 in the Institute of Physics and German Physical Society's New Journal of Physics, the researchers used a method known as "plasmonic cloaking" to hide an 18-centimetre cylindrical tube from microwaves.
Some of the most recent breakthroughs in the field of invisibility cloaking have focussed on using transformation-based metamaterials -- inhomogeneous, human-made materials that have the ability to bend light around objects -- however, this new approach uses a different type of artificial material -- plasmonic metamaterials.
When light strikes an object, it rebounds off its surface towards another direction, just like throwing a tennis ball against a wall. The reason we see objects is because light rays bounce off materials towards our eyes and our eyes are able to process the information.
Due to their unique properties, plasmonic metamaterials have the opposite scattering effect to everyday materials.
"When the scattered fields from the cloak and the object interfere, they cancel each other out and the overall effect is transparency and invisibility at all angles of observation.
"One of the advantages of the plasmonic cloaking technique is its robustness and moderately broad bandwidth of operation, superior to conventional cloaks based on transformation metamaterials. This made our experiment more robust to possible imperfections, which is particularly important when cloaking a 3D object in free-space," said study co-author Professor Andrea Alu.
In this instance, the cylindrical tube was cloaked with a shell of plasmonic metamaterial to make it appear invisible. The system was tested by directing microwaves towards the cloaked cylinder and mapping the resulting scattering both around the object and in the far-field. The cloak showed optimal functionality when the microwaves were at a frequency of 3.1 gigahertz and over a moderately broad bandwidth.
The researchers, from the University of Texas at Austin, have shown in previous studies that the shape of the object is irrelevant; oddly shaped and asymmetric objects can both be cloaked using this technique.
Moving forward, one of the key challenges for the researchers will be to demonstrate the cloaking of a 3D object using visible light.
"In principle, this technique could be used to cloak light; in fact, some plasmonic materials are naturally available at optical frequencies. However, the size of the objects that can be efficiently cloaked with this method scales with the wavelength of operation, so when applied to optical frequencies we may be able to efficiently stop the scattering of micrometre-sized objects.
"Still, cloaking small objects may be exciting for a variety of applications. For instance, we are currently investigating the application of these concepts to cloak a microscope tip at optical frequencies. This may greatly benefit biomedical and optical near-field measurements," continued Professor Alu.
http://www.sciencedaily.com/releases...0125195535.htm

FREE PAPER:-

Rainwater, D., A. Kerkhoff, et al. (2012). "Experimental verification of three-dimensional plasmonic cloaking in free-space." New Journal of Physics 14(1): 013054.
Quote:
We report the experimental verification of metamaterial cloaking for a 3D object in free space. We apply the plasmonic cloaking technique, based on scattering cancellation, to suppress microwave scattering from a finite-length dielectric cylinder. We verify that scattering suppression is obtained all around the object in the near- and far-field and for different incidence angles, validating our measurements with analytical results and full-wave simulations. Our near-field and far-field measurements confirm that realistic and robust plasmonic metamaterial cloaks may be realized for elongated 3D objects with moderate transverse cross-section at microwave frequencies.
http://iopscience.iop.org/1367-2630/14/1/013054/
__________________
The religious are not necessarily insane, but oft look to it as a state of considerable virtue.
Reply With Quote
Reply

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time now is 01:23 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2014, vBulletin Solutions, Inc.