Tech Weave

Invisibility Cloak

An invisibility cloak that works in the microwave region of the electromagnetic spectrum has been unveiled by researchers in the US. The device is the first practical version of a theoretical set-up first suggested in a paper published earlier in 2006.

The cloak works by steering microwave light around an object, making it appear to an observer as if it were not there at all. Materials that bend light in this way do not exist naturally, so have to be engineered with the necessary optical properties.

In recent years, materials scientists have made rapid progress in making so-called "metamaterials", which can have exotic electromagnetic properties unseen in nature. These are made up of repeating structures of simple electronic components such as capacitors and inductors.

To study the effect of his cloak,images of microwaves flowing through the rings, like water waves moving across a pond were taken. Without the cloak in place, the microwaves were reflected and diffracted by the copper ring. But with the cloak in place, the distortion was dramatically reduced.

Slight distortion
If you could see in the microwave region of the spectrum, the copper ring would not quite disappear. You'd see perhaps a shadow and some slight distortion where the copper ring ought to be.

The device has another important limitation – it works only at a single specific frequency of microwave. Hopes to build a 3D structure that could hide an object completely from view are a possibility to look into.

So far, the technology works only in the microwave region of the spectrum. The problem with visible light is that it has a much smaller wavelength, meaning an optical metamaterial would have to be built on the nanoscale, which is beyond the limits of current nanotechnology. It, too, would only work at a specific frequency.

posted by Vandana Bhatia @ 8:55 PM