Tuesday, April 8, 2014

Illuminating LED History


Carl Accardo, one of the men who explained the phenomenon of electroluminescence in 1951, has passed at the age of 85.


Most of us don't get big obituaries in big newspapers, let alone one that highlights an important contribution to LED development. Carl Accardo died in March 2014, and the headline in the Boston Globe noted his important LED research.



A newly-minted MIT physicist, Accardo worked at the United States Signal Research and Development Laboratory in the late 1940s. With Kurt Lehovec and Edward Jamgochian, he co-authored a 1951 paper titled Injected Light Emission of Silicon Carbide Crystals. The paper was part of a small post-war wave of research into photonics. In Electronic Concepts, Jerrold Krenz credits the trio with verifying in the lab the phenomenon that Oleg Lasev identified as electroluminescence. (Lasev's name is variously transliterated as Lossew and Lossev.)


Phenomena in search of an application

Last year, Pervalz Lodhie provided us with an outline of the history of LED technology. He noted that we didn't see great attention or advances in what we regard as LEDs until the 1960s. Light-emitting diodes didn't begin to enter the public lexicon until the mid-1970s. It took several decades before a significant convergence of research and technology brought LEDs to a point of usefulness for some of the applications we see today.


Lehovec continued his research in integrated circuits and collected many patents in semiconductors and LEDs. Of note, neither of the others made LED technology their life's work. After receiving his master's from NYU, Accardo went on to a career as a geophysicist and as an executive with MIT's Industrial Liaison Program. His work on the latter project led to the Order of the Sacred Treasure, Gold Rays with Rosette award, one of the highest honors awarded by the Japanese government. Jamgochian received a 1964 patent for a more sophisticated accelerometer.


Accardo's work moved LED technology forward. Nearly 50 years later, Lehovec, Accardo, and Jamgochian's paper was valued enough to be included in the SPIE Milestone Series volume on phosphors, light emitting diodes, and scintillators. Not bad for a short-term project.


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