It all began in 1916 where Albert Einstein laid the foundation for the invention of the laser and the maser, in a ground-breaking experiment involving Max Planck's law of radiation based on the concepts of spontaneous and induced emission. The theory was forgotten until after World War II.
It wasn't till 1953, Charles H. Townes, James P. Gordon and Herbert J. Zeiger produced the first maser, a device operating on similar principles to the laser, but producing microwave rather than optical radiation.
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