Flat lens can create a perfect image

An ultrathin, flat lens with a nanometer-thick layer of gold can focus light without imparting the distortions of conventional lenses, U.S. engineers say. The flat lens is essentially two-dimensional at only 60 nanometers thickness but focusing power approaches the ultimate physical limit determined by the laws of light diffraction, Harvard University researchers reported Thursday. A very thin wafer of silicon is plated with a nanometer-thick layer of gold, which is stripped away in places leaving behind an array of V-shaped structures. When a laser is shone onto the flat lens, the structures act as nanoantennas that capture incoming light and hold onto it briefly before releasing it again. Those delays, precisely tuned across the surface of the lens, change the direction of the light in the same way that a thick glass lens would. However, the flat lens eliminates optical distortions such as the "fish-eye" effect that results from conventional wide-angle lenses. Operating at wavelengths commonly used in fiber-optic communications, the new device is completely scalable, from near-infrared to terahertz wavelengths, and simple to manufacture, the researchers said. "In the future we can potentially replace all the bulk [lens] components in the majority of optical systems with just flat surfaces," study lead author Francesco Aieta, a visiting graduate student from the Universita Politecnica delle Marche in Italy, said. "It certainly captures the imagination."