Friday, March 23, 2007

Superlenses and Smaller Computer Chips

Continued from page 1

By Kevin Bullis

Only the Berkeley researchers, however, demonstrated the ability to see an actual image: first two parallel lines, and then the letters O and N. To make their lens, the researchers carved a half-cylinder shape out of a piece of quartz, leaving behind a U-shaped valley. They then deposited alternating layers of silver and aluminum oxide, each just 35 nanometers thick, with each layer curved by the quartz scaffold.

The purpose of this arrangement is to capture a type of light wave, called an evanescent wave, that comes from the smallest details of a surface. Ordinarily, such waves decay too quickly to be seen with an ordinary light microscope. But because of the lens's novel materials and structure, the wave doesn't decay as long at it is inside the lens. The image carried by the wave is then magnified by the curved form of the lens layers, making it possible to see the image with an optical microscope.

So far the lens, because it's cylindrical, can only be used to see things lined up along the bottom of its U-shaped valley. The researchers are developing a spherical version that would allow them to see a whole surface at once--a prerequisite for both optical movies and for photolithography.

Still, much research remains. The new lens's resolution is limited in part by the absorption of light by metal, says David Smith, professor of electrical and computer engineering at Duke University. Also, in the current design, the surface to be imaged has to be pressed right up against the lens; otherwise, the evanescent waves decay. That limits the lens's applications. For example, it could not be used to improve a telescope.

Nevertheless, Smith, who himself works on metamaterials, says that the results of the three papers are encouraging. "It's a great indication as to how this field is flourishing to see three such papers published in the same issue," he says.