Photonics are a kind of technology that uses photons, the quanta of light, as electronics uses electrons. As photons travel at the Universe’s speed limit and do not need a medium to move, photonics can perform operations very quickly while using little power. Several components will have to be made and/or improved before we can see photonic computers on the market. Researchers at the Joint Quantum Institute, University of Maryland, and NIST have recently made an exceptional optical switch that could potentially lead to photonic transistors.
This switch holds a quantum dot in a resonant cavity which is contained in a waveguide that blocks all but a small frequency range of light. The researchers were able to direct the movement of an information-carrying beam with a second control beam. When the information beam enters the cavity with the quantum dot, it is normally deflected, but if the control beam enters the cavity simultaneously the dot reacts and allows the information beam to pass through.
Optical switches have been made before, but this one uses five times less power than the previous record; 90 attojoules (90*10-18 J). With the light at the near-infrared wavelength of just 921 nm, this translates to just 140 photons being needed to operate the switch. The switch is also very fast, needing only 120 picoseconds (120*10-12 s) to change.
While this is an important step for photonics it is not quite an optical transistor. The switch is not able to modulate a light beam with only a weak control pulse. Also it has to be cooled to just 40 K. Still, this is a great accomplishment and could lead to more. Though 140 photons were needed for this setup, in theory the design needs only 6 photons to manipulate the switch. Perhaps that will be achieved next.