Invisiblity Cloaks Jump Into The Third Dimension

Invisibility cloaks took a step from science fiction to science fact this past weekend. A team of German scientists announced the construction of the first material that renders objects invisible in three dimensions.

The field of transformation optics has made tremendous strides in the last few years towards invisibility by harnessing metamaterials, minuscule artificial structures that react to light in ways that are impossible for natural materials. Although the science is (extremely) involved, these metamaterials essentially route light waves around the object they encase in such a way that the waves appear undistorted, as though nothing was there. Previous experiments only worked in two dimensions - essentially, the objects were only invisible as long as they were observed exactly straight ahead. Moving even slightly to the side would reveal the hidden object.

Scientists tend to bristle when the popular media throws around terms like "invisibility cloak", so you know it's a big deal when the research team behind this latest project actually calls their paper, "Three-Dimensional Invisibility Cloak at Optical Wavelengths." Led by Tolga Ergin and Nicolas Stenger of Germany's Karlsruhe Institute of Technology, the team built upon previous experiments but refined the fabrication techniques such that the hidden object would remain invisible from viewing angles up to sixty degrees.

In a podcast interview with Science, Ergin explained what his team had accomplished by recounting their experiment:

Imagine you would have a mirror and this mirror has a little bump in it and you can hide something underneath this bump. But of course you would still see the bump as the reflected image is distorted because of the bump. So what we did is put the cloaking structure on top of this bump so the mirror again appears flat. So you cannot tell that there actually is something beneath that mirror.

This new experiment also moved closer to the invisibility cloaks of science fiction in another crucial respect. Previous cloaks were only invisible in microwave wavelengths, meaning they were still visible to the naked eye. Ergin and Stenger's material is also invisible in infrared wavelengths, a breakthrough that takes the field one step closer to creating cloaks that are invisible to human observers.

The dimensions of the experiment were tiny - the invisible object was only a few microns wide - but the team believes scaling their material upward to conceal larger objects could just be a matter of time. As Stenger explains:

"Theoretically, it would be possible to do this on a large scale but technically, it's totally impossible with the knowledge we have know. But it could become a reality in 10 years."

It's still early days in the field of making things invisible, but this breakthrough appears to represent significant progress in realizing one of the most fantastical elements of science fiction. It's your move, teleportation.

[Science]