![The "newest" invisibility cloaking device is constructed of optically clear calcite crystals.](http://cdn2-b.examiner.com/sites/default/files/styles/image_content_width/hash/bf/a3/bfa3d9a9abf2490c5c3c2e4ef6b41a6c.jpg?itok=9NK5VfZf "The "newest" invisibility cloaking device is constructed of optically clear calcite crystals.")
You have probably seen the amazing video of the invisibility cloaking crystal from the TED Talks 2013. We can't embed the video for you just yet so please use the first link. The video demo caught us by surprise today, March 1, 2013. The reports give credit to Dr. Baile Zhang for the demonstration at TED. It takes some moving a piece of plastic around with tweezers to "see" the cloaking effect. It's not exactly a Harry Potter or Star Trek style cloak. And it does not appear to be exactly new either. Sorry kids, but the invention was published in 2011 in Physical Review Letters.
Thorough credit is given to the inventor team in the PRL document. Currently left out of the news reports is Dr. George Barbastathis, the other members and the MIT 3D Optical Systems Group. The current device does not appear to be patented but the two doctors currently hold some 69 U. S. patents. It may be that this invisibility device is not patentable - at least one other team appears to have made a similar development. However, the/these devices are relatively unique in that they do seem to cloak solid objects in visible light. This is accomplished with simple calcite crystals (that happen to be clear, of course) in the current TED demo.
Um, the PRL document reports that a mirror and a liquid medium were used to achieve this effect. We admit that a mirror is not apparent in the new demo video (linked above), but the tweezers might indicate that the thing is in some liquid medium. If you look carefully you will observe a small triangular groove or cavity along the bottom of the cloaking device. More about the device and the technology was revealed at the Jan. 2011 SMART conference. Dr. Barbastathis explained that they had the crystal portions assembled and glued together for about $1000. Not prohibitive but that should prevent the local shade-tree inventor from making their own.
It's not a complete all visible wavelength 3D cloak but still demonstrates how invisibility occurs in transformation optics. Also important is that the optic axes line up. Of further importance to the effect is optical anisotropy - which is common to (joined?) calcite crystals. For more on invisibility cloaks see our blog post "An invisibility cloak (DIY, sort of)".
