IBM Scientists Develop Silicon Chip that Slows Down Light
IT News Online Staff
2005-11-03
IBM announced that its researchers have created a tiny perforated silicon chip called a "photonic crystal waveguide" that is able to slow light down to less than 1/300th of its usual speed.
IBM's scientists were able to do this directing light down a channel of perforated silicon. The chip's design also enabled the scientists to vary the speed of light over a wide range simply by applying an electrical voltage to the waveguide.
The company said the device represented a big advance toward the eventual use of light in place of electricity in the connection of electronic components, potentially leading to vast improvements in the performance of computers and other electronic systems.
IBM said that this was the first time researchers have been able to actively control the light speed on a silicon chip, using standard silicon with standard micro- and nanoelectronic fabrication technology. The company said the device's small size, use of standard semiconductor materials, and ability to more closely control this "slow light" could make the technology useful for building ultra-compact optical communications circuits that are practical for integration into computer systems.
"This work is an example of our continued commitment to push the limits of exploratory science," said Dr. T.C. Chen, vice president of Science and Technology for IBM Research. "We are constantly exploring new technologies that might enhance our systems and storage products. We believe this brings real value to both our clients, who rely on these products to enhance their business, and to their customers, who ultimately benefit from the new and improved services they make possible."
The IBM team succeeded using a photonic crystal waveguide, a thin slab of silicon punctuated by regular arrays of holes that scatter light. The pattern and size of the holes gives the material a very high refractive index, the higher the refractive index, the slower the light. Heating the waveguide locally with a small electrical current alters the refractive index, allowing the speed of light to be quickly tuned over a large range with very low applied electric power.
IBM said the work done by its researchers could help solve a number of issues currently being faced in the industry such as the inability to more quickly move information around within electronic systems, which is one of the biggest bottlenecks in electronic design today. The technology could in future enable light to be used to speed communication between the components within a computer. The components to support such an optical network need to provide excellent control over the light signal as well as very small and inexpensive to manufacture, and IBM's silicon chip addresses these issues.
The active area of the IBM device is microscopically small, indicating the possibility of complex light-based circuits with footprints not much larger than semiconductor circuits. The manufacturing processes used to build the device are available in nearly any semiconductor factory. IBM said the silicon chip could be applied to create a variety of nanophotonic components such as optical delay lines, optical buffers and even optical memory, all of which would be useful in building computer systems knitted together by powerful optical communications networks.
IBM's research work was partially supported by the Defense advanced Research Agency (DARPA) through the Defense Sciences Office program "Slowing, Storing and Processing Light".
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