Friday, June 7, 2013

Human-Scale Invisibility Cloak Unveiled

Researchers demonstrate an invisibility cloak that can be scaled to almost any size and say it could be used to hide orbiting satellites.

In the last decade or so, invisibility cloaks have captured the imagination of researchers and the public alike. The excitement is based on two advances.

The first is the idea of “transformation optics”–the ability to bend light around a region of space to make it look as if it weren’t there. The second is the creation of metamaterials, synthetic substances with optical properties unknown in nature that can be designed to achieve this goal.

One of the goals in this area is to create a Harry Potter-style cloak capable of hiding a human at all optical frequencies in all directions. A bonus would be the ability to make this device as big or small as required so that it can hide objects of any size.

Achieving all these features is currently impossible. There is always a compromise. The first cloak worked only at a single microwave frequency. More recent cloaks work over the entire a range of optical frequencies but can only hide tiny objects over a limited viewing angle.

Today, John Howell at the University of Rochester in New York, and Benjamin Howell, show how to make simple cloaks that hide huge objects over the entire optical spectrum, albeit with a significant compromise. One of their devices is big enough to cloak a person.

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