Tuesday, May 26, 2009

Friday, May 1, 2009

on the wishlist

full story

Invisibility cloak edges closer

Tiny holes all over the cloak bend the light around the bump
Scientists have rendered objects invisible under near-infrared light.
Unlike previous such "cloaks", the new work does not employ metals, which introduce losses of light and result in imperfect cloaking.
Because the approach can be scaled down further in size, researchers say this is a major step towards a cloak that would work for visible light.
One of the research teams describes its miniature "carpet cloak" in the journal Nature Materials.
This "carpet" design was based on a theory first described by John Pendry, from Imperial College London, in 2008.
Michal Lipson and her team at Cornell University demonstrated a cloak based on the concept.
Xiang Zhang, professor of mechanical engineering at the University of California, Berkeley, led the other team.
"Essentially, we are transforming a straight line of light into a curved line around the cloak, so you don't perceive any change in its pathway," he explained.
This is not the first time an invisibility cloak has been made, but previous designs have used metals, whereas the carpet cloak is built using a dielectric - or insulating material - which absorbs far less light.
"Metals introduce a lot of loss, or reduce the light intensity," said Professor Zhang. This loss can leave a darkened spot in the place of the cloaked object.
So using silicon, a material that absorbs very little light, is a "big step forward," he says.