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Achivements of Robert Hall

Robert Hall invented the version of the magnetron that operates most microwave ovens, the semiconductor laser found in compact disk players, and power rectifiers that greatly improved power transmission efficiency.

His basic rectifier structure, with silicon replacing the germanium, is used today for AC-to-DC power conversion in electric locomotives and high-voltage DC electrical transmission. In 1962 Hall invented the semiconductor injection laser, a device now used in all compact disk players and laser printers, and most optical fiber communications systems.

However he worked not alone. Hall’s laser project team included Dick Carlson, Gunther Fenner, Jack Kingsley, and Ted Soltys. Whereas other groups thinking about semiconductor lasers had proposed to use a macroscopic “external cavity” into which a GaAs diode was placed, Hall decided to polish parallel faces onto his GaAs diodes so that the Fabry- Perot optical cavity geometry was built into the device. This approach was not universally applied and, in fact, the importance of optical feedback into the diode “active region” was not fully appreciated by many workers. Hall’s team operated their first successful GaAs laser diodes under pulsed conditions at 77K on September 16, 1962.

A schematic diagram of Hall’s early concept for an injection laser is shown in Figure. The first verification of laser operation was made through the observation of the near and far-field interference patterns using an infrared up converting “snooper scope” which was being used in Hall’s lab to study the emission from such infrared light emitters.