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Wires of Light

Photonic wiring between transistors could make faster chips, while photons zipping between chips could turbo-charge your computer’s motherboard. Imagine thousands of laser beams crisscrossing within your computer, and you wouldn’t be far off.

Engineers at companies such as Honeywell, Sun Microsystems and IBM, as well as at universities around the world, are already testing arrays of light-emitting diodes and laser beams that could serve as the “bus” that transports information across a motherboard from microprocessors to memory chips to display screen and back. Initial applications for these systems will be in high-end computing. Honeywell, for example, is using optical interconnects to link microprocessors, creating compact, powerful parallel computers.

Squeezing light inside individual computer chips to replace metal interconnects may not be far behind. The ability to etch smaller transistors on silicon wafers has steadily increased the power of computers. The problem is that as transistors get smaller and smaller, they can switch much faster than they can communicate with each other, slowing down the overall functioning of the chip. While chip makers think they can squeeze out enough performance from the shrinking metal wires that connect electronic devices to make the next generation of chips, they are turning to photons for future batches. Sematech, the international association of semiconductor makers, estimates that its members will begin to exhaust improvements to metal interconnects by 2008. The use of light-based interconnects is one of the few feasible solutions, according to Sematech.

Optical interconnects in computing “is still speculative,” says David A.B. Miller, an electrical engineer at Stanford University. But, he predicts, you’ll see such interconnects “in mainstream computing by the end of the decade. That’s not a ridiculous statement to make.”

Whether working on telecom or computing applications, however, the ultimate goal of optics researchers is to make integrated microphotonic circuits as ubiquitous as today’s microelectronic chips. “The ideal solution is to have something able to do the mirror function, the switching function and the waveguiding function all within one platform,” says Shawn Lin, a physicist at Sandia National Laboratories in Albuquerque, N.M. Lin is using photonic crystals, tiny silicon-based structures that confine light with exquisite efficiency, to make his own set of lasers, amplifiers, waveguides and other devices for lightwave circuits. Getting all of these devices to work together on a single wafer, says Lin, will put photonics on “holy ground,” just as moving the electron from a vacuum to the silicon wafer unleashed the power of electronics. What’s more, Lin thinks integration will take hold in photonics much faster than in microelectronics.

Lin’s voice falls to a whisper as he discusses the future of microphotonics, as if revealing the full potential of capturing light on a chip could somehow jinx his chances for success. “All the necessary inventions, the materials issues have been solved,” says Lin. “It’s up to our imagination to come up with innovative devices and to build the basic building blocks. There are large amounts of money just waiting to see breakthroughs happen.”

Those breakthroughs are likely to come from the dozens of industrial and university labs that are working on integrated photonics, as materials scientists like Lin work with optical theorists to perfect waveguides, lasers and other basic building blocks, fabrication experts figure out how to integrate these devices in a high-density chip, and systems engineers optimize circuitry. Just as today’s micromirrors and tiny bubbles are beginning to switch on the full potential of the Internet’s high-speed optical backbone, tomorrow’s optical chips promise to unleash the photon’s raw power and speed to fundamentally change how information is transmitted.

Building Tomorrow’s Optical Internet Company Recent Moves Strategy Alcatel No major acquisitions Already a leading player in DWDM, the telecom giant is spending heavily on R&D to develop optical devices Cisco Systems Bought ArrowPoint Communications (May 2000) for $5.7 billion; Pirelli Optical Systems (Dec. 1999) for $2.15 billion; Monterey Networks (Aug. 1999) for $500 million Gained Internet switching technology from ArrowPoint; DWDM technology and optical switching devices from the Pirelli and Monterey acquisitions Ciena
Acquired Lightera Networks (March 1999) for $552 million An early pioneer in DWDM, looking for a business comeback by providing intelligent optical switching Corvis Testing its all-optical devices with Broadwing Communications Leverage technology for ultra-long optical transmission and optical switching to provide an all-optical network Lucent Technologies Micromirror-based optical switch is scheduled to be installed this year Relying on internal R&D to develop optical devices; a leader in microelectromechanical systems Nortel Networks Bought Qtera (Dec. 1999) for $3.25 billion; Xros (March 2000) for $3.25 billion; CoreTek (March 2000) for $1.43 billion Spending heavily to acquire the necessary technologies to put together an all- optical Internet

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