IBM controls light speed

Staff -- Control Engineering, 1/1/2006

Light's speed can be slowed in dispersive materials. IBM scientists have successfully slowed light to 3.3% of its normal 186,000-miles/sec speed with a bit of silicon called a crystal waveguide.

Researchers created waveguides with conventional chip-manufacturing processes by fabricating 200-mm silicon-on-insulator wafers with 2-µm-thick buried-oxide and 220-nm-thick silicon layer. A periodic hole array, with a triangular lattice, was written in the resist layer with electron beam lithography.

Using a 2-milliwatt heater with the waveguide, the scientists could also control light's speed effectively in about 100 nanoseconds. The light was slowed additionally by applying an electric field to the waveguide.

Pulses of "slow" light could carry data efficiently for all-optical storage and switching. Furthermore, the technology has the potential to allow computers to substitute light for electricity and run at terahertz speeds.

Historically optical components tended to be large and pricey—defying the economies of large-scale production. Some see the manufacture of optical components as much art as science.

A crystal waveguide would allow optical components to be scaled down resulting in significant cost savings. Moreover, manufacturing waveguides from silicon would allow a merging of the optics and the electronics on the same silicon chip. Nearly concurrently, another group of scientists announced a new silicon-based microtransmitter that can send optical data at 100 Gbps or 10% of a terahertz. www.ibm.com