Transfomation optics were used recently to develop an improved invisibility cloak with a 100-fold increase in area compared to previous visible-wavelength cloaks. The new design from Purdue University uses a relatively inexpensive glass and gold waveguide that achieved a more economical design using transformation optics. An inexpensive waveguide directs light around cloaked objects (center) so that even a laser bends around it to emerge on the other side with no shadow cast. Other invisibility cloaks use optical diffraction gratings that tune into specific wavelengths with a negative index of refraction that allows the cloak to provide invisibility, but only at those wavelengths. The Purdue device was formed from two gold-coated surfaces, one a curved lens, the other a flat sheet. The result was a broadband cloak, working at a wide swath of wavelengths simultaneously, enabling it to shield an area covering the entire spectrum of visible light. The demonstration showed how a laser benda around the cloaked area, leaving no shadow, even though the area was 100 times larger than the wavelength of the laser.
Text: http://www.eetimes.com/showArticle.jhtml?articleID=217600639
