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First Exciton Integrated Circuit Built

Exciton ICs would negate the need to convert optical data to electrons and back again

2 min read

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.

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The Transistor at 75

The past, present, and future of the modern world’s most important invention

2 min read
A photo of a birthday cake with 75 written on it.
Lisa Sheehan

Seventy-five years is a long time. It’s so long that most of us don’t remember a time before the transistor, and long enough for many engineers to have devoted entire careers to its use and development. In honor of this most important of technological achievements, this issue’s package of articles explores the transistor’s historical journey and potential future.

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