After plugging away for some time at two dimensional invisibility cloaks, researchers have begun experimenting with a cloak that can obscure its contents in three dimensions. While the device only works in a limited range of wavelengths, its relative success should help keep the field moving forward.

The invisibility cloaks mentioned among scientists are not really turning anything invisible, but rather playing tricks with the light, misdirecting it so that the objects they encase cannot be seen. Normally, the cloaks only work in two dimensions, so just by changing your point of view a bit, the cloak will become obvious—a limitation scientists want to overcome. The 3D cloak in this case is made of woodpile-structured photonic crystals that can redirect light of wavelengths around the size of the crystals' rod spacing.

Researchers spread the cloak over a trough-like depression in a gold sheet over a glass surface. They found that while the crystals couldn't hide the trough perfectly, they were able to significantly diminish its presence, even when the point of view was shifted. However, the cloak was only able to misdirect light in the 1.5 to 2.6 micrometer range, corresponding to near infrared rays.

While crystals tailored to the visible range would do little to fool the human eye, a infrared cloak could probably fool a security detection system pretty easily. At any rate, it could at least make the object it covers look more like an anomaly than an approaching threat.

Science, 2010. DOI: 10.1126/science.1186351 (About DOIs).