Monday, May 23, 2005

"OPTICAL: Metamaterials yield left-handed complement for optics"

Metamaterials that are able to reverse basic optical properties of conventional lenses and microwave antennas are being explored as a superior optical medium. Normal materials refract electromagnetic radiation by bending it away from the angle of incidence, which requires that lenses be convex in order to focus. Left-handed metamaterials, on the other hand, bend light toward the angle of incidence, thereby enabling a planar lens to focus radiation to a point. "Using left-handed metamaterials, we can build novel, smaller, lighter-weight lenses, sensors and antenna systems than those that are available today," said Srinivas Sridhar, a professor at Northeastern University. "Besides cheaper and better, our form factor is also more flexible, because metamaterials can conform to odd shapes since they are composed mostly of air. In our experiment, we used a periodic array of aluminum-oxide rods in air laid out in a lattice like a photonic crystal." Sridhar performed the work with research associates Patanjali Parimi and Wentao Luj as well as doctoral candidate Plarenta Vodo. The "meta" in metamaterials means they substitute macroscopic objects-rods in this case-for atoms in a macrosized, crystalline-like lattice. The pitch of the lattice's grid sets the wavelength affected. Unlike normal lenses, that wavelength can be set to an arbitrarily small subwavelength, giving the lens a nearly infinite focusing and resolution capability.