IBM Lights Up Nanotubes
The results were published in the May 2 issue of Science. The paper analyzes the test results, comparing them with theoretical models to establish that the nanotube did indeed create light, at a wavelength of roughly 1,500 nanometers.
So far, no one's saying this is the future replacement for telecom lasers. The nanotube is an incoherent light source -- it emits in essentially random directions and therefore would be unsuitable for optical communications (see our Beginners' Guide: Laser Basics).
It seems probable that nanotubes could be used to create a laser, but it's going to take a lot more research. "If one needs more light power, one could use these bundles with mirrors at the ends, and hopefully it could lase," says Phaedon Avouris, manager of nanoscale science for IBM Research in Yorktown Heights, N.Y.
More immediate uses for nanotube light would be in close-quarter situations, such as on-chip interconnects. But Avouris stresses that any applications are a long way off.
Carbon nanotubes are long, skinny molecules constructed of carbon atoms. Their diameter is just one or two nanometers, while their length can be more than a micrometer, a disparity that makes the critters practically one-dimensional.
Nanotubes often get mentioned as a possible successor to silicon transistors in integrated circuits. It's assumed there is a limit to how small circuitry can get on silicon, and companies such as IBM and NEC Corp. (Nasdaq: NIPNY) are probing carbon nanotubes, which can behave as transistors -- as a possible next step (see NEC Gets Nanotubular).
IBM appears to be the first to turn a nanotube into a light source, however. Other research has generated light from a nanotube, but only with the help of a laser.
IBM's experiment involved simultaneously injecting one end of the tube with electrons and the other end with "holes" -- positively-charged analogues to electrons. When the two flows meet, they neutralize one another. "In the process, the energy can be either dissipated as heat or as light," Avouris says.
Because the molecule can act as a transistor, the light can be turned on and off, and its intensity can be varied. And Photon Avouris believes it likely that different wavelengths can be generated using different diameters of nanotube.
— Craig Matsumoto, Senior Editor, Light Reading