Alfred Kastler (born 03.05.1902) is a French physicist and a member of the Paris Academy of Sciences (1964). He was born in Guebwiller. He graduated from the École Normale (1926). In 1931-36 he worked at the University of Bordeaux, in 1936 —38 at the University of Clermont-Ferrand, in 1938 —41 he was professor at the University of Bordeaux, and in 1941 —68 at the École Normale.
His research was in the field of optics, atomic spectroscopy and quantum electronics. He studied the excited optical states of atoms by the method of optical resonance, which became the basis for the development of the system of optical pumping that he discovered in 1952. In 1951 he showed in general form that spin-lattice relaxation can be studied by means of a magneto-optical technique (the Faraday effect), noting that there is a direct connection between electron paramagnetic resonance and magneto-optical effects. He analysed the simplest cases in which paramagnetic resonance shows itself in the spectra of magneto-optical activity. He studied a great many quantum transitions of atoms, coherent effects and other matters. His work became the basis for the creation of masers and lasers and was awarded the Nobel Prize (1966).
He founded a school of physicists.