Branching of stationary inversion states in a cavity-pumped paramagnetic maser amplifier

The nonlinear dynamics in a paramagnetic maser amplifier is investigated experimentally and theoretically under conditions such that the active medium exerts a sufficiently strong feedback influence on the pump field to induce population inversion of the spin levels. Branching of the inversion ratio due to the onset of bistability in the nonlinear microwave cavity of the pump at a frequency of 150 GHz is observed experimentally. Conditions are determined for the possible excitation of new nonlinear resonances when the spin system is inverted by a standing-wave field, and the stability of the resulting stationary nonequilibrium states of the paramagnet is analyzed. Zh. Tekh. Fiz. 69, 101–105 (May 1999)