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In most modern computers, electrons travel between transistor switches on metal wires or traces to gather process and store information. The optical computers of the future will instead use photons traveling on optical fibers or thin films to perform these functions. But entirely optical computer systems are still far into the future. Right now scientists are focusing on developing hybrids by combining electronics with photonics. Electro-optic hybrids were first made possible around 1978, when researchers realized that photons could respond to electrons through certain media such as lithium niobate (LiNbO3). To make the thin polymer films for electro-optic applications, NASA scientists dissolve a monomer (the building block of a polymer) in an organic solvent. This solution is then put into a growth cell with a quartz window. An ultraviolet lamp shining through this window creates a chemical reaction, causing a thin polymer film to deposit on the quartz.
An ultraviolet lamp causes the entire quartz surface to become coated, but shining a laser through the quartz can cause the polymer to deposit in specific patterns. Because a laser is a thin beam of focused light, it can be used to draw exact lines. A laser beam's focus can be as small as a micron-sized spot (1 micron is 1-millionth of a meter, or 1/25,000 of an inch), so scientists can deposit the organic materials on the quartz in very sophisticated patterns. By painting with light, scientists can create optical circuits that may one day replace the electronics currently used in computers.
In the optical computer of the future electronic circuits and wires will be replaced by a few optical fibers and films, making the systems more efficient with no interference, more cost effective, lighter and more compact.
The thin films allow us to transmit information using light. And because we're working with light, we're working with the speed of light without generating as much heat as electrons. We can move information faster than electronic circuits, and without the need to remove damaging heat.
Multiple frequencies of light can travel through optical components without interference, allowing photonic devices to process multiple streams of data simultaneously. And the optical components permit a much higher data rate for any one of these streams than electrical conductors. Complex programs that take 100 to 1,000 hours to process on modern electronic computers could eventually take an hour or less on photonic computers.
The speed of computers becomes a pressing problem as electronic circuits reach their maximum limit in network communications. The growth of the Internet demands faster speeds and larger bandwidths than electronic circuits can provide. Electronic switching limits network speeds to about 50 gigabits per second (1 gigabit (GB) is 1 billion bits). Terabit speeds are already needed to accommodate the 10 to 15 percent per month growth rate of the Internet, and the increasing demand for bandwidth-intensive data such as digital video (1 TB is 1 trillion bits). All optical switching using optical materials can relieve the escalating problem of bandwidth limitations imposed by electronics.
Last year Lucent Technologies' Bell Laboratory introduced technology with the capacity to carry the entire world's Internet traffic simultaneously over a single optical cable. Optical computers will someday eliminate the need for the enormous tangle of wires used in electronic computers today. Optical computers will be more compact and yet will have faster speeds, larger bandwidths and more capabilities than modern electronic computers.
Optical components like the thin-films developed by NASA are essential for
the development of these advanced computers. By developing components for
electro-optic hybrids in the present, NASA scientists are helping to make
possible the amazing optical computers that will someday dominate the future. |
