Light-Speed Computer Chips via Carbon Nanotubes

Could carbon nanotubes enable the first optical computer chips?

In the time it takes to snap your fingers, light travels around the world seven times. On a large scale, fiber optics are already used to transmit data via this incredibly fast and energy efficient medium. Now, small-scale applications will be able to transmit ever-increasing amounts of data in the same manner. Computer chips of the near future will reach light-speed thanks to a recent development involving waveguides and carbon nanotubes. Together, they can convert electric signals into clearly defined optical signals.

Constructing Nanoscale Photonic Devices

Engineering researchers achieved this feat by installing carbon nanotubes 1 micrometer in length by 1 nanometer in diameter on metal contacts transverse to the wave guide. The researchers accomplished this using dielectrophoresis, the movement of uncharged particles toward the position of maximum field strength in an unevenly charged electric field. Through this process, the carbon nanotubes were deposited from solution and arranged vertically to the waveguide. This method is highly effective for transferring nanoscale objects to carrier materials.

The carbon nanotubes integrated into the waveguide serve as a small light source. Upon the application of electric voltage, they produce photons. A tiny compact switch element converts the electrical signals into clear optical signals.

Processing the Waveguide

The way in which the waveguide is processed determines the wavelength at which light is transmitted. Waveguides several micrometers long are provided with fine, nanoscale cavities with engravings using electron beam lithography, which determines the waveguide’s optical properties. Similar to colorful butterfly wings, the resulting photonic crystals reflect light in certain colors.

Carbon nanotube above a photonic crystal waveguide with electrodes. The structure converts electric signals into light. (Image courtesy of KIT.)

The result of this application is more than just a pretty effect. The tiny converter for changing an electrical signal to an optical one is bringing us closer to the future of computing. This converter compacts photons to the extent of a laser and responds to changing signals very rapidly. Even in this early laboratory stage, the researchers are producing light signals from electric signals in the gigahertz frequency range. Light-speed chips mean computers which are significantly faster than ever before, opening up a world of potential for future computing power.

The researchers involved in this project were Ralph Krupke from the KIT Institute of Nanotechnology and Materials Science, Wolfram H.P. Pernice from the University of Munster (formerly KIT) and Manfred M. Kappes from the Institute of Physical Chemistry and Institute of Nanotechnology at KIT.

The findings of this research can be found in Nature Photonics. For other insights into the future of computing check out this brain-inspired neurosynaptic processor from IBM.