Infrared and Optical Masers
A. L. Schawlow and C. H. Townes
Physical Review, Vol. 112, pp. 1940-1949, December 15, 1958.
Reprinted in: F. S. Barnes (Editor), "Laser Theory", pp. 47-56, IEEE Press, 1972.
Townes shared the 1964 Nobel Prize in physics for this work with Nikolai Basov and Aleksander Prokhorov. Later, Schawlow shared the 1981 Nobel Prize in physics for research done with lasers. Note how, in the title of the paper, the authors used the old definition of the word "Optical" in making it synonymous with the word "Visible". Infrared Masers, later to be called Infrared Lasers, were distinct from Optical Masers or Lasers. Nowadays, the word "Optical" is all-embracing and covers the entire electromagnetic spectrum from the far-infrared to the ultra-violet. It is this latter modern definition that is used extensively on this web site.
Copyright (c), Physical Review 1958, IEEE 1972