Abstract

If so inclined, one might trace photoelectric mixing back to at least 1883, when Righi [1] demonstrated experimentally that a beam of light, split into two beams and frequency shifted relative to each other produced moving fringes when recombined, which he interpreted as beating. By 1947 Forrester, Parkins and Gerjuoy [2] had proposed that even light from two different, and thus completely incoherent, sources could be made to produce beats, and Gorelik [3] had pointed out that the output current from a fast photo-detector, when illuminated by a single spectral line should contain frequency components up to approximately the spectral linewidth. Forrester, Gudmundsen and Johnson [4] silenced all critics when they detected the beat note between two Zeeman components of the 5461 Å line of Mercury in 1955, and by 1959 Raman [5] had described a time-dependent speckle pattern observed by scattering light from a thin film of milk illuminated by a narrow beam of light from a Mercury arc lamp.

© 1996 Optical Society of America