Millimeter-wave range masers: A review

The paper surveys work done on millimeter-wave traveling-wave masers in the USSR, USA, and Sweden, mainly in the 1970's. Particular consideration is given to: the physical principles and characteristics of traveling-wave masers; the search for and investigation of active media; the design of electrodynamic systems for the interaction of the active medium with microwave fields; the establishment of conditions of stable amplification; and the development of such elements as nonreciprocal components, pumping sources, and transmission lines. The current status and future prospects of the physics and technology of masers are briefly examined.