Exciton circuits

Researchers in the US have brought us one step closer to the practical integration of optical and electronic circuitry on a chip. A semiconductor device that can perform logic operations with both light and electronics, could lead to significantly smaller optoelectronic devices which would also benefit from a reduction in power requirements and an increase in speed, as compared with today's state of the art technology.

They demonstrated an integrated circuit (IC) consisting of three exciton optoelectronic transistors (EXOT's). These components function as switches in much the same way that electronic transistors do, but rather than enabling a current to flow when a voltage is applied, exciton flux is allowed to flow from one end of the device to another. Excitons, which are bound pairs of electrons and holes, are produced by photons from light incident at the input which, when they recombine at the output, emit a photon. The light can effectively be manipulated electronically and thereby perform computational operations, by using exciton flux as the intermediate medium.

The team demonstrated various optical switching and merging functions that the device was capable of. The results from their research were recently published in the journal Science¹ and reported on elsewhere^2,3.

1) A. A. High, E. E. Novitskaya, L. V. Butov, M. Hanson, A. C. Gossard, Science, 19 June 2008 (DOI: 10.1126/science.1157845).

2) 'Excitonic integrated circuit' is a first - Device used excitons to switch beams of light [Physics World]

3) Exciton-Based Circuits Eliminate A ‘Speed Trap’ Between Computing And Communication Signals - Particles called excitons that emit a flash of light as they decay could be used for a new form of computing better suited to fast communication, physicists at UC San Diego have demonstrated. [Science Daily]