Researchers at IBM Corp. have developed the world's first optical chip able to electrically control the speed of light.

IBM claims its optical silicon chip can electrically alter the effective index of refraction of an integrated photonic-crystal waveguide. The experimental component could make possible tunable optical delay-line chips, optical buffers, high-extinction optical switches, and highly efficient wavelength converters, the company says.

Together with other optical components, such devices could eliminate the telecommunications industry's reliance on optical-to-electrical and electrical-to-optical converters. The optical chip can variably slow light by a factor of 300, under active control by a low-power (under 2 mW), fast-changing, (less than 100-nsec) electrical signal.

The chip was constructed using ordinary silicon-on-insulator CMOS fabrication techniques, the team says. The active element is a 250- m-long photonic-crystal waveguide formed with a nanoscale version of micromachining. researchers perforated a 223-nm-thick membrane with holes 109 nm in diameter, spaced at a 437-nm pitch. As a result, the waveguide slows light passing through it in a 20-nm bandwidth at the communications wavelength of 1,620 nm.