Theory of Cavity Masers

Simple interference experiments identify correlation functions which describe the response of maser amplifiers and the output of maser oscillators. General operator techniques are used to evaluate these functions in cavity maser systems for which the coupling of the maser electromagnetic field to external energy sources or sinks is mediated by systems whose short-term response depends primarily upon average or macroscopic system properties. The dielectric theory which results includes only those short-term non-linearities associated with the external pumping fields. In the long term both the external and the cavity fields can modify the susceptibility functions. The techniques utilized permit a detailed analysis of approximations and suggest generalizations for increased precision. As one important result of this type the theory indicates that macroscopic rate equations are valid if modulation frequencies are much less than the width of the narrowest coupling system spectral line.