From the Labs: Materials

Tiny Lasers
The smallest laser ever could find uses in future computers.

Source: “Demonstration of a spaser-based nanolaser”
Mikhail A. Noginov et al.
Nature 460: 1110-1112

Results: A new laser devised by researchers at Norfolk State University, Purdue, and Cornell is the smallest ever made: it consists of a nanoparticle just 44 nanometers in diameter. It can emit both photons and plasmons, which are waves that travel along the surface of metals.

Why it matters: The research is the first demonstration of a spaser, a device that some physicists believe will form the basis of future optical computers. Such computers have the potential to be much faster than today’s electronics, but current optical devices are bulky because photons are difficult to confine. Light in the form of plasmons can be confined to much tighter spaces, allowing for very fast, compact chips. Though researchers have previously made devices that can rout plasmons on chips, this spaser is the first device that can generate and amplify them.

Methods: To make the laser, the researchers coated a gold nanosphere with a layer of silica that’s embedded with dye. The gold provides the medium where the plasmons form; in the dyed silica layer, plasmons excited by light from a pumping laser are amplified, much as photons are amplified in the mirrored cavity of a conventional laser. The amplified plasmons then escape to travel along a metal surface, or they can be converted to photons so that the device emits a laser light. Either way, the device produces waves with the frequency of green light.

Next steps: The spasers could be improved by modifying them to emit different wavelengths. Spasers that work in the infrared, for example, might be useful for telecommunications.

Source: “Impact of Anode Microstructure on Solid Oxide Fuel Cells”
Toshio Suzuki et al.
Science 325: 852-855

Results: Japanese researchers lowered the operating temperature of solid-oxide fuel cells by changing the structure of their electrode materials. They improved the power output of the cells at 600 °C by an order of magnitude.

Why it matters: Solid-oxide fuel cells can efficiently convert a variety of fuels, such as hydrogen and diesel, into electricity. But because they typically operate at temperatures above 700 °C, they require expensive materials, wear out relatively quickly, and are limited to stationary applications. Compared with other approaches to lowering the operating temperature of fuel cells, the new method has the advantage of using conventional materials that are relatively inexpensive. The new fuel cells could eventually be useful as auxiliary power sources to extend the range of electric vehicles, among other applications.

Methods: The researchers used established processes to fabricate tubular fuel cells 1.9 millimeters in diameter. To produce anodes with different structures, they heat-treated the tubes–which consist of a zirconia-based ceramic and a nickel-oxide mixture–at three temperatures lower than those ordinarily used in fuel-cell production. The resulting anodes were unusually porous, which proved to increase the performance of fuel cells based on them.

Next steps: The researchers established that they can bundle the microtubular fuel cells, but they need to develop ways to turn the bundles into modules that generate enough power for commercial applications.