Wednesday, June 12 2013
a) Shadow behind metal cylinder under plane wave illumination; b) front reconstruction after passing cylinder cloaked by thin multilayer dielectric; c) total scattering cross width for cloaked & bare cylinders. (b) & (c) demonstrate the cloaking
Michigan Technological University’s invisibility cloak researchers have moved the bar on one of the holy grails of physics – making objects invisible. Just last month, Elena Semouchkina, an associate professor of electrical and computer engineering at Michigan Tech, and her graduate student, Xiaohui Wang, reported successful experimental demonstration of the use of non-conductive ceramic metamaterials to cloak cylindrical objects from microwave-length electromagnetic waves. Previously, Semouchkina had designed a non-conductive glass metamaterial cloak that worked with infrared frequency waves, which are shorter than microwaves.
Scarcely had the ink dried on their report when they developed a different cloaking approach. This time, they used ordinary dielectric materials such as ceramics having differing dielectric permittivity — a measure of the response of a substance to an electrical field — instead of metamaterials, which are artificial materials with properties not found in nature. They found that they were able to cloak larger cylindrical objects and cloak them more effectively than they had using metamaterials.
According to their latest report, Semouchkina and Wang designed a new kind of cloak that uses a very thin multilayer dielectric coating made of natural material, not metamaterial. They compared it through mathematical analysis and computer simulations to a metamaterial cloak of similar size but based on a different principle, called transformation optics.
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