20 June 2008—Researchers at the University of California, San Diego, say they’ve made an experimental integrated circuit that operates using excitons—basically energized electrons bound to positively charged counterparts called holes, which form when light hits a semiconductor. The group’s results were detailed 19 June in the online version of Science . If the technology could be commercialized, it could speed computing and communications by better integrating electronic circuits and optical data communications.
Computers process signals using electrons, but most data communication outside the computer happens via photons. Because light cannot be easily manipulated with electric fields, the light signals are usually first converted to electrical signals by a photodiode, processed in the computer, and then converted to light again using a laser and other optical components for transport—an inefficient scheme. Excitons, however, directly interact with electric fields, eliminating the need for all the conversion steps and making for potentially faster and more energy-efficient computing.
When the photon signal enters the chip, it instantly transforms into excitons. The exciton signal is processed by the circuit and automatically transforms back to photons at the output. ”You start with the photonic signal and end with the photonic signal,” says Leonid Butov, a physics professor at UC San Diego and author of the study.