Optical Transistors

Electronics work by controlling and using the flow of electrons throughout a circuit. But imagine if, instead of electrons, you could build a "photonic" circuit that controlled and responded to the flow of photons with the same level of control. Such a theory is nothing new, but an upcoming article in Physical Review Letters (by G. A. Wurtz, R. Pollard, and A.V. Zayats) may have a breakthrough in the technology...

All-optical circuit components are light-based analogues of electrical transistors and other devices. They are among the most eagerly anticipated technological advances, with the potential to revolutionize computers and communications. But all-optical devices built in the past have been far too large and power hungry to be practical. Physicists at the Queen’s University in Belfast appear to have solved the problems with a prototype optical amplifier that is both small and low power. The key to the device is a layer of gold film pierced by an array of holes 0.2 millionths of a meter in diameter and coated in a layer of polymer. The researchers shine two beams of light on the structure: a signal beam and a control beam. When the beams strike the patterned film they produce plasmons, which are essentially blobs of electron gas near the surface of a metal. Varying the intensity and the color of the control beam causes the plasmons to interact in ways that enhance or decrease the transmission of the signal beam through the film. That is, the film acts as an all-optical transistor, with the potential to serve as a building block in optical circuits and optical versions of microelectronic devices.
-- American Physical Society press release