Researchers at the IBM Thomas J. Watson Research Center in Yorktown Heights, N.Y., have reported the emission of electrically driven polarized infrared radiation from ambipolar field-effect transistors consisting of single or bundled semiconducting single-walled carbon nanotubes. They reported the development, which has potential applications in the production of ultrasmall photonic devices, in the May 2 issue of Science.To fabricate the emitters, they deposited the approximately 1.4-nm-diameter nanotubes from solution onto a P-type silicon substrate covered with a layer of silicon dioxide. Titanium source and drain electrodes were built atop individual nanotubes, and a 10-nm-thick layer of silicon dioxide capped the structures. Although the devices produced radiation just outside the L-band at approximately 1650 nm, the wavelength of the emission should be controllable by employing nanotubes of different diameters.