Getting Light to Bend Backwards

While developing new lenses for next-generation sensors, researchers have crafted a layered material that causes light to refract, or bend, in a manner nature never intended.

Refraction always bends light one way, as one can see in the illusion of a “bent” drinking straw when observed through the side of a glass. A new metamaterial crafted from alternating layers of semiconductors (indium-gallium-arsenic and aluminum-indium-arsenic) acts as a single lens that refracts light in the opposite direction.

Refraction is the reason that lenses have to be curved, a trait that limits image resolution. With the new metamaterial, flat lenses are possible, theoretically allowing microscopes to capture images of objects as small as a strand of DNA. The current metamaterial lens works with infrared light, but the researchers hope the technology will expand to other wavelengths in the future.

Earlier efforts have crafted metamaterials that bend light in a similar way, but this is the first to do so using a 3-dimensional structure and a metamaterial comprised entirely of semiconductors. Those traits will prove critical for incorporating the technology into devices such as chemical threat sensors, communications equipment and medical diagnostics tools.

The paper describing the technology appeared online Oct. 14, 2007, in Nature Materials.

The research was developed primarily at NSF's Mid-Infrared Technologies for Health and the Environment Engineering Research Center and NSF's Princeton Center for Complex Materials Materials Research Science and Engineering Center.

Additional information is available in the Princeton University press release at: http://www.princeton.edu/main/news/archive/S19/21/37O65/