Photon amplification in a two-photon lossless micromaser

We investigate the interaction of atoms through two-photon resonant transitions, with quantized cavity radiation, in the framework of a lossless micromaser theory. Taking advantage of the fact that the atomic inversion is quasiregular in time in this model, with quite precise revivals, we find a very strong amplification of the average photon number. At the two-photon revival time, the atom leaves the cavity in an almost pure state. This leads to an essentially noise-free process that results in a shift of two photons of the initial photon distribution each time an atom passes through the cavity, while the width of the photon distribution remains constant. This leads to strongly sub-Poissonian field statistics.