A two-cavity unilateral maser amplifier

A unidirectional quantum-mechanical amplifier has been developed in which the amplifying medium consists of a beam of ammonia molecules passing through, in turn, two separated resonant cavities. The cavities are electrically isolated from one another so that the only coupling is provided by the molecular beam. Unlike the various single-cavity amplifiers constructed in other laboratories, in which a common coupling point for input and output signals necessitates the inclusion of isolators or circulators to separate the two signals, the amplifier described herein affords a natural isolation of input and output with independent control of loadings. After a discussion of the physical principles underlying the mechanism of amplification in a two-cavity molecular beam amplifier, a simplified theory of the operation of the two-cavity amplifier is presented, outlining the parameters which influence power gain and noise Figure. The details of an experimental amplifier are described and the results of gain and noise figure measurements are reported.