As described in today's issue of the journal Nature, IBM scientists were able to slow light down to less than 1/300th of its usual speed by directing it down a channel of perforated silicon called a "photonic crystal waveguide." The design of the device allows the light's speed to be varied simply by applying an electrical voltage to the waveguide.

Researchers have known for some years how to slow light to a crawl under laboratory conditions, but IBM claims that actively controlling the light speed on a silicon chip, using standard silicon, represents a first for the research community.

IBM hopes the device's small size, use of standard semiconductor materials, and ability to control this "slow light" could make the technology useful for building compact optical-communications circuits 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."

While chip performance has continued to increase, electronic systems don't always reap the full benefits. Just as traffic congestion can hinder commerce by limiting the flow of products and materials within a busy city, the inability to move information around within electronic systems quickly is one of the biggest bottlenecks in electronic design today. The work announced by IBM could help relieve some of the constraints associated with conventional computer technology.

Scientists have searched for practical ways to use light to speed communication between the components within a computer. But, to be practical, the components to support such an optical network will need to provide excellent control over the light signal, while also being very small and inexpensive to manufacture.

The photonic crystal waveguide used in the research is a thin slab of silicon punctuated by 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 with a small electrical current alters the refractive index, allowing the speed of light to be tuned over a large range with very low applied electric power .

The active area of the device is microscopically small, which IBM claims will create new possibilities for light-based circuits with footprints not much larger than semiconductor circuits. IBM said the manufacturing processes used to build the device are available in nearly any semiconductor factory.