Nature Photonics: A Light Source For Faster Chips

Waveguides with integrated carbon nanotubes for converting electrical signals into light / faster computer chips are possible / publication in Nature Photonics

Worldwide growing amounts of data, the conventional electronic processing have reached their limits. The future information technology therefore uses light as a medium for fast data transmission even within computer chips. Researchers led by the KIT have now shown that tiny carbon tubes are as on-chip light source for the information technology of tomorrow, if one uses nanostructured waveguide to obtain appropriate lighting characteristics. Their results are the scientists in Nature Photonics before now. 

Broadly, the communication is by light long life: fiber optic cable transmitted as an optical waveguide, for example, telephone and Internet signals. On the way, the advantages of light, ie speed and energy efficiency in future to be able in miniature, at the level of computer chips, use, researchers have made an important step towards the application at KIT thanks basic research. By including tiny carbon tubes in a nanostructured waveguide they have developed a compact miniaturized circuit part which converts electrical signals into optical signals clearly defined.

"The nanostructures act as a photonic crystal, and allow the properties of the light from the tube tailor", explained Felix Pyatkov and Valentin Fütterling, the authors of the study, the research at the Institute of Nanotechnology of the KIT. "So we can produce very narrow-band light in the desired color on the chip." In what wavelength light is passed, is precisely defined by the processing of the waveguide: The Engraving using electron beam lithography of several micrometers receives long waveguide finest cavities of a few nanometers size which determine its optical properties. The resulting photonic crystal reflects light in certain colors, a phenomenon that can be observed in nature on colorful appearing butterfly wings.

As new light sources, carbon nanotubes of approximately one micron long and one nanometer in diameter are positioned transversely to the waveguide on metal contacts. At KIT, a process has been developed, with which it is possible to selectively incorporate the nanotubes in highly complex structures. The researchers used the method of dielectrophoresis to accomplish that which is about a nanometer in diameter - a millionth of a millimeter - to deposit large carbon tubes from a solution and arrange perpendicular to the waveguide. This originally from biology possibility for separation of particles using inhomogeneous electric fields is well suited to deposit nanoscale objects on support materials. The directly introduced into the waveguide carbon nanotubes act as tiny light source because they produce photons when voltage is applied.

The newly introduced compact current-light signal converter fulfills the requirements for the next generation of computers that connect electronic components with nanophotonic waveguides. The transducer concentrates the light almost as strong as a laser and speaks at high speed on variable signals. Already can be generated from electrical signals light signals in the gigahertz frequency range using the developed by researchers opto-electronic components.

At the research project were Ralph Krupke, a researcher at the Institute of Nanotechnology of the KIT and at the Institute of Materials Science of TU Darmstadt, tungsten HP Pernice, who moved a year ago from KIT to the Westfälische Wilhelms-Universität Münster, and Manfred M. Kappes, Institute of Physical Chemistry and Institute of nanotechnology of the KIT, spearheaded. Funded it was through the program Science and Technology of Nano Systems (STN) of the Helmholtz Association, whose aim is to explore nanosystems with unique functionality and to tap the potential of materials with feature sizes of a few nanometers. The Volkswagen Foundation funded the research project a PhD position, beyond the high-tech platform Karlsruhe Nano Micro Facility supported (KNMF) the project.

The Karlsruhe Institute of Technology (KIT) connects its three core tasks of research, teaching and innovation on a mission. With around 9 300 employees and 25 000 students, KIT is one of the great scientific and engineering research and education institutions in Europe.