Princeton (NJ) - Scientists have engineered a new type of "metamaterial" which exhibits optical properties exactly opposite of those in nature. Whereas light passing through naturally occurring materials has a positive index of refraction, this new material has a negative index. This makes it bend the wrong way, or in the opposite direction to natural light. This unnatural ability is being researched and could have profound implications to everyday life.
The physical material is made out of semiconductor components : sand, basically. It is arranged in a complex array of specifically deposited bits of materials. These comprise operational layers by design which then exhibit desired properties. This arrangement process creates a new class of materials scientists are calling metamaterials. These ultra-small materials could almost be thought of as custom-built molecular arrangements (though using larger blocks of component materials), sometimes completely contrary to anything found in nature. They are assembled bit by bit, piece by piece, until the final material is available for testing. In this particular instance of a metamaterial, the scientists found properties which really surprised them. All electromagnetic radiation, including visible light, bends in a particular way when passing through or near naturally occurring materials. This is what makes eyeglasses and magnifying glasses work, what makes the bottom of a pool look bent and distorted if viewed from the surface as the ever changing shape of waves alters the extent to which light is bent. It’s even what makes the scenery behind a hot source on a cool day appear distorted, or what makes the road turn into sky off in the distance. It’s all because light is bending and reaching our eyes after the bend.
In everyday life, that bend is predictable. We can use a particular type of material in our eyeglasses, for example, because our science has shown that with this material light will bend in such a way as to correct nearsightedness. Another arrangement will bend light to correct farsightedness. These follow curved surface shapes which vary throughout their radii, allowing light entering our eye through the different curves to be corrected for our malfunctioning eye focus. But, such correction often distorts the visual appearance of whatever we’re looking at. And for those with significant eye problems, rather observably. Objects, especially those near the edges, appear bent or twisted, sometimes to extremes. Sometimes they also apear smaller than they actually are, or straight lines appear bent. With this new material that effect may no longer be necessary, according to scientists.
Princeton researchers are looking at these very peculiar properties of the new material and are discovering all kinds of new uses for it. Imagine eyeglasses that could be flat. Or infrared cameras that could be significantly smaller than they are today, due to the ability to notably refract infrared’s long wavelength easily. Scientists are even talking about ways to correct the pathways of ultra-small visible light sources with this new material. This would allow optical observance of molecules or DNA directly, according to the researchers. We would see with new microscopes the ultra-small world because the light would not be distorted so significantly when being refracted and focused. Telescopes would also benefit in similar ways, allowing more to be seen more accurately with less effort.
Research is also continuing on this and other materials. Scientists are now trying to dope the current material to find out if they can introduce other unique properties. The team believes that there could be profound implications in the areas of optical, infrared and laser research in the years to come. New types of optics could be constructed which allow for better focusing, smaller distortions, less loss of photons through scattering or absorption, etc., even allowing devices which, through infrared detection, allow human breath to be analyzed for trace gases or substance emission. This could include early, passive detection for diabetes and lung disease, according to researchers. Future optical computers might also benefit.
The project is funded by the National Science Foundation and the research was carried out at the MIRTHE center as well as the Princeton Center for Complex Materials. The scientific team was led by a graduate student named Anthony Hoffman. The team also included Leonid Alekseyev, Scott Howard, Kale Franz ; Dan Wasserman, Evgenii Narimanov as well as collaborators from Oregon State University and telecommunications firm Alcatel-Lucent. Full details of the project were published this week in a scientific journal called Natural Materials.