Electronic Design

ORNL's Optical Switches May Dethrone Electronic Transistors

The Department of Energy's Oak Ridge National Laboratory (ORNL) in Tennessee is developing an all-optical transistor that may eventually replace electronic transistors. ORNL's micromechanical quantum detector is a highly sensitive miniature photon-detection device based on photo-induced stresses in semiconductors. By using photons instead of electrons, scientists can develop a transistor that's 100 times faster than anything available today.

So far, optical transistors haven't been practical. Typically, optical designs require tradeoffs in throughput versus rejection efficiency, cost, speed, and size. But ORNL's model uses a diode laser LED that causes optical absorption of waveguide material. The absorption of light produces stress, which strains the material and makes it move. This in turn causes a switch to turn on or off. Or, it can redirect light coming from one end onto two or more channels (see the figure). In effect, it's equivalent to a switch or modulator used in conventional transistors.

So far, this effect has been produced with frequencies in the 1-MHz range. This is significant because devices can be thermally driven to just 1000 Hz. Researchers expect this photon-driven transistor to be at least 100 times faster than a conventional electron-driven transistor. Such performance could have a significant effect on fiber-optic communications, sensing, and computation processing applications.

Like conventional electron semiconductors, these devices would be tuned to achieve specific results by modeling physical and geometrical properties. Mass production using microelectronics fabrication methods could drive the price of these devices well below $100, while including more capabilities and functionality than other devices that cost over $20,000.

For more information, visit ORNL's web site at www.ornl.gov.

TAGS: Components
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