Invisibility cloak sci-fi dream no more

Scientists have taken a step further in making an invisibility cloak by developing a material that renders objects invisible to near-infrared light. Two teams of scientists from Cornell University and UC Berkeley have reportedly developed invisibility cloaks using a new technology that can hide objects across optical wavelengths. Previous such "cloaks" had metals in their structure which resulted in imperfect cloaking due to loss of light. However, the new technology is the first cloak built considered to be carpet-based, as it uses a dielectric - or insulating material - which absorbs far less light than previous invisibility cloaks designed using metals. "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," explained Xiang Zhang, professor of mechanical engineering at Berkeley, who led one of the teams. "Metals introduce a lot of loss, or reduce the light intensity," said Professor Zhang said. This loss can leave a darkened spot in the place of the cloaked object. The cloak changes the local density of the object it is covering, Zhang further explained. He told BBC News that when light passes from air into water it would be bent, because the optical density, or refraction index, of the glass is different to air. "So by manipulating the optical density of an object, you can transform the light path from a straight line to any path you want," he added. The new material produces such an effect through a series of minuscule holes strategically "drilled" into a sheet of silicon.