Researchers have reported a material that will bring the scientists closer to the “invisibility cloak”.
This research has been done by researchers at the University of Texas in Austin and published online the New journal of Physics.
Researchers have successfully hide (cloaked) an 18-centimetre (7.2-inch) cylindrical tube from light by placing it in the microwave part of the spectrum of energy meaning the tube is invisible from any angle in the microwave region of the electromagnetic spectrum but not in the visible light region i.e. light in higher frequencies, and human eye perceives light in higher frequencies. As reported in the paper, cloaking worked best at a microwave frequency of 3.1 GHz.
Researchers have given a proof of a principle that so-called plasmonic meta-materials can achieve the cloaking effect. Plasmonic meta-materials are made up of metals and non-conductive synthetics composed of nanometer-sized structures, which are very much smaller than the wavelength of light striking them causing the incoming photons to excite currents making the light waves scatter.
In this research, researchers have made a shell of plasmonic meta-materials and placed a cylinder inside. They then expose the combination to microwaves. The microwaves scattered by the shell ran into microwaves bounced back from the object, thus preventing the return signal to the viewer.
“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 observations,” said co-lead investigator Andrea Alu.
According to Alu, a war-plane could be hid from radar microwaves in all directions by using this material. “What we are thinking about is not necessarily cloaking the whole warplane but some hot spots, a part such as the tailplane that you would want to cloak because it reflects most of the energy (from microwave radar).”
D Rainwater, A Kerkhoff, K Melin, J C Soric, G Moreno and A Alu`, (2012). Experimental verification of three-dimensional plasmonic cloaking in free-space. New journal of Physics, doi:10.1088/1367-2630/14/1/01305