When Alan Huang revealed his plans to build an optical computer, most of his * fellow scientists dismissed the idea as hopelessly quixotic. It was impractical, if not impossible, they said, to create a general-purpose computer that could use pulses of light rather than electrical signals to process data. During one of Huang's lectures on the subject, a third of the audience walked out. At another talk, some of the scientists in attendance laughed and heckled the researcher, calling him a quack and a dreamer. Recalls the 41-year-old engineer at AT&T Bell Laboratories: "I began to have computer nightmares, but I never doubted that it could be done. I wanted the last laugh."
That was several years ago. Few of the doubters were smirking last week when Huang and AT&T unveiled an experimental computing machine based on optics rather than electrons, the first of its kind. The device -- a crudely configured collection of lasers, lenses and prisms -- could serve as the basis for future optical computers 100 to 1,000 times as powerful as today's most potent supercomputers. The potential applications are stunning: robots that can see; computers that can design aircraft from scratch; processors that can swiftly convert spoken words into written text and vice versa. Such practical optical computers are still years -- some would say light-years -- away. Yet many scientists are already predicting that the device will have an impact similar to that of the integrated circuit, which made small personal computers possible. David Casasent, director of Carnegie Mellon University's Center for Optical Computing, calls Huang's work "an important first step" that has "advanced the clock" of the new technology.
Photons, the basic unit of light beams, can in theory be much better than electrons for moving signals through a computer. For one thing, photons can travel about ten times as fast as electrons. And while electrons react with one another, beams of photons, which have no mass or charge, can cross through one another without interference. Thus while electrons must be confined to guide wires, photons can move in free space. This could open the door to radically new and different computer designs, including so-called parallel processors that could work on more than one problem at a time instead of one after another, as today's serial computers do.
But harnessing the computing power of light has proved to be a daunting challenge. The earliest attempts to build an optical computer date back to the late 1950s, when researchers experimented with mercury-arc lamps and even sunlight. Not much happened until the early 1960s brought the invention of lasers, devices that could concentrate light into powerful, high-precision beams. IBM spent four years and $100 million trying to develop a machine that could use laser beams to operate the multiple "on-off" switches that are the heart of all computers. Unfortunately, the switching operations required too much energy, and the devices often overheated. Eventually the company virtually abandoned the project as unfeasible.