Light powered computers

Last Christmas, Dr Mario Pannicia received a gift not even Santa Claus could deliver. He and his colleagues at Intel8217;s Silicon Photonic...

Last Christmas, Dr Mario Pannicia received a gift not even Santa Claus could deliver. He and his colleagues at Intel8217;s Silicon Photonics Lab succeeded in making the first laser out of silicon, the stuff of ordinary computer chips. He immediately called in outside experts to confirm the finding, and spent the rest of the holiday banging out a paper, which was published a month later in the scientific journal Nature.

Pannicia and his colleagues aren8217;t the only researchers celebrating. While optical computing was heralded more than 10 years ago as the next quantum leap in information technology, scientists had until recently failed to deliver on that promise. Now, a spate of new discoveries may finally allow engineers to build computers that handle information in the form of light rather than electricity.

Superiority of light over electricity for carrying reams of information has long been appreciated. In the 1970s, telephone companies replaced copper transmission cables with ones of optical fibres, and today the backbone of the Internet is sent through the fibres as pulses of light. The problem is when those pulses reach their destination: they must be converted to electricity before a computer can use them.

Many scientists have held that the obvious solution8212;to make optical chips out of silicon, which is cheap8212;would never work because silicon isn8217;t very good at conducting light. But a few engineers kept slogging away. One of them was Intel8217;s Pannicia, who figured out how to get silicon to emit laser light. He and his colleagues etched a tiny path in the silicon to conduct light using specially designed mirrors. Initially, the lasers wouldn8217;t work because the chips got clogged with electrons. Pannicia8217;s team found a way to 8216;8216;flush out8217;8217; the electrons with a vacuum and a strong positive charge, and ended up doubling the laser8217;s strength.

Meanwhile, scientists at IBM8217;s research labs in Yorktown Heights, New York, designed a tiny device that can slow down photons particles of light on a silicon chip to less than one three-hundredths of their normal speed by directing them down a buffer of silicon pathways, punctured with holes to allow the light to scatter. This buffer allows the chip to slow photons down without losing data encoded on them.

Then, in October, researchers at Stanford University came up with a modulator to control photon traffic in a chip by switching light on and off up to 100 billion times a second. With such precise control of photons, scientists can deal with the traffic congestion from increased data flow. This will allow engineers to connect chips in a computer with optical fibres rather than copper wires, which are a speed bottleneck. Top communications equipment today can transmit 10 billion bits of data a second; these chips could reach up to 100 billion bits a second.

What this means, researchers believe, is that computers will be up to 100 times faster than they are now. That would allow you to download movies in seconds and instantly search gigabytes of information. It would also enable much more powerful medical gadgets, more precise enivronmental monitoring devices and better wireless communications. Researchers caution, however, that it may take five or 10 years for these advances to make it out of the labs and into products.

Newsweek