Semiconductor diode that produces visible or infrared light when subjected to an electric current, as a result of electroluminescence. Visible-light LEDs are used in many electronic devices as indicator lamps (e.g., an on/off indicator) and, when arranged in a matrix, to spell out letters or numbers on alphanumeric displays. Infrared LEDs are used in optoelectronics (e.g., in auto-focus cameras and television remote controls) and as light sources in some long-range fibre-optic communications systems. LEDs are formed by the so-called III-V compound semiconductors related to gallium arsenide. They consume little power and are long-lasting and inexpensive.
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However, electrically pumped VECSELs (another matter entirely), were the brainchild of Aram Mooradian, a well-known and highly credentialed worker in the laser field. (Mooradian worked for many years at MIT Lincoln Laboratory in Lexington, Massachusetts. He is known for fundamental contributions to diode laser linewidth studies.) Mooradian formed a company, Novalux, Inc., for this express purpose (www.novalux.com) which was the first to demonstrate VECSELs (which they call "NECSELs"). Applications for electrically pumped VECSELs include frequency doubling of near-IR VECSEL emitters to attain compact powerful sources of single-mode blue and green light for projection display purposes.
In a VECSEL, the external mirror permits a significantly greater area of the diode to participate in generating light in a single mode, resulting in much higher power than otherwise attainable. Monolithic VCSELs emit powers in the low milliwatt range. By contrast, at the 2004 Optical Society of America "Conference on Lasers and Electro-Optics," held in San Francisco, California, one company (Coherent, Inc.) announced 45 watt continuous wave single-mode emission from an optically pumped VECSEL. Numerous other companies and organizations world-wide have adopted the optically pumped architecture for its simplicity.