A kinetic theory of the two-photon absorption from a single mode of the radiation field is presented. It is found that, in general, the rate of two-photon absorption depends on certain correlation functions, and hence on the coherence properties, of the field. The results are applied to the case of a pure coherent state and the case of a chaotic field.

• Received 27 September 1965

DOI:https://doi.org/10.1103/PhysRev.144.1081