Visible Light Enters the Bizarro World

From Science:

Invisible They’re still a ways off, but invisibility cloaks and microscopes with superresolution could now be a big step closer to reality thanks to a pair of results to be reported this week. For 8 years, physicists and engineers have tinkered with metamaterials, patterned arrays of bits of metal and insulator that bend and manipulate microwaves and shorter wavelength radiation in strange ways. Now, a team has made three-dimensional miniaturized metamaterials that work with near-infrared and visible light. That’s a key step toward superlenses and cloaks for visible light, some say. Others say the claims are overblown.

Metamaterials put a kink in the way light usually passes from one medium into another. Suppose light from the setting sun shines on a pond. As light waves strike the surface, their direction will change so that they flow more directly down into the water. (See diagram.) Such “refraction” arises because the light travels more slowly in water than in air, giving water a higher “index of refraction.” Still, the light continues to flow from west to east. Were water a “left-handed metamaterial,” however, the light would undergo “negative refractions” and bend back toward the west. Refraction is the key to how ordinary lenses focus light, and in theory, negative refraction would allow a flat slab of metamaterial to function as a lens that could focus light infinitely tightly.

Physicists unveiled the first left-handed metamaterial for microwaves in 2000. Looking a bit like a high-schooler’s science-fair project, it was an assemblage of metallic rods and rings that interacted with and bent microwaves in strange ways. Since then, researchers have been pushing to shorter and shorter wavelengths, and with the new studies, the visible realm is within sight. On Thursday online in Nature, Xiang Zhang, an engineer at the University of California, Berkeley, and colleagues will describe a metamaterial that works for near-infrared light and, unlike previous materials for such light, is three-dimensional.

More here.