A Circularly Polarized Maser Oscillator

Abstract

The frequency stability of a circularly polarized solid-state paramagnetic maser oscillator has been observed with the objective of obtaining the information needed to construct a frequency standard with a broad microwave spectral line. The beat frequency between two such masers by using ruby can be made almost free from the variation of the static magnetic field and of the angle between the crystalline axes and the static magnetic field. The stability of the 1.5-Mc beat frequency is approximately 10−6 for short time intervals, and is approximately 10−5 for long time intervals. The short-time stability is limited mainly by the fluctuation of the cavity resonant frequency in the liquid helium. The long-time stability is determined by the drift of the pump frequency, although the reason for this interrelation is not thoroughly understood. The effect of reflections from the load on frequency is considerably reduced by the unidirectional structure used here, as compared with that to be expected with a reflection type of maser. We also show that the unidirectional maser amplifier can be built with reduced cross section by utilizing dielectric-loaded circular waveguide.