Researchers from Princeton University have created an easy-to-produce material from semiconductors that has the rare ability to bend light in the opposite direction from all naturally occurring materials. This could lead to advances in high-speed communications, medical diagnostics, and detection of terrorist threats.
The new substance is in a relatively new class of materials called metamaterials, which are made out of traditional substances such as metals or semiconductors, arranged in very small alternating patterns that modify their collective properties. This enables metamaterials to manipulate light in ways that cannot be accomplished by normal materials. Previous metamaterials were two-dimensional arrangements of metals, which limited their usefulness. The Princeton material is the first three-dimensional metamaterial constructed entirely from semiconductors.
Light waves bend whenever they pass from one medium to another, a phenomenon called refraction. Lenses in reading glasses or a camera work because of refraction. All materials have an index of refraction, which measures the degree and direction that light is bent as it passes through them. While materials found in nature have positive refractive indices, the Princeton material has a negative index of refraction.
Negative refraction holds promise for the development of superior lenses. The positive refractive indices of normal materials necessitate the use of curved lenses, which distort some of the light that passes through them. Flat lenses made from materials with negative refraction could lead to far more powerful microscopes that can see things as small as molecules of DNA.