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First edition, compolete journal issue in original printed wrappers, of the first proposal for the construction of a laser. Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. It describes any device that creates and amplifies a narrow, focused beam of light whose photons are coherent. In a laser, the atoms or molecules of the lasing medium either a crystal like ruby or garnet, or a gas or liquid are pumped, so that more of them are at higher energy levels than at the ground state. The end result is a sudden burst of coherent light as the atoms discharge in a rapid chain reaction. This process is called stimulated emission. Albert Einstein first broached the possibility of stimulated emission in a 1917 paper, having turned his attention the year before from general relativity to the interplay of matter and radiation, and how the two could achieve thermal equilibrium. Einstein devised an improved fundamental statistical theory of heat, embracing the quantum of energy. First, Einstein proposed that an excited atom in isolation can return to a lower energy state by emitting photons, a process he dubbed spontaneous emission. Spontaneous emission sets the scale for all radiative interactions, such as absorption and stimulated emission. Atoms will only absorb photons of the correct wavelength: the photon disappears and the atom goes to a higher energy state, setting the stage for spontaneous emission. Second, his theory predicted that as light passes through a substance, it could stimulate the emission of more light. Einstein postulated that photons prefer to travel together in the same state. If one has a large collection of atoms containing a great deal of excess energy, they will be ready to emit a photon randomly. However, if a stray photon of the correct wavelength passes by (or, in the case of a laser, is fired at an atom already in an excited state), its presence will stimulate the atoms to release their photons early and those photons will travel in the same direction with the identical frequency and phase as the original stray photon. A cascading effect ensues: as the crowd of identical photons moves through the rest of the atoms, ever more photons will be emitted from their atoms to join them" (APS). Townes shared the 1964 Nobel Prize in physics for "fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser-laser principle". Schawlow shared the 1981 Nobel Prize in physics for his "contribution to the development of laser spectroscopy". Large 8vo, pp. 1829-2181. Original printed wrappers (lower outer corner gently bumped, spine slightly sunned).
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