Induced superradiation for a collection of three-level atoms

N three-level atoms interact simultaneously with classical and quantum fields, which are in quasiresonance with various atomic transitions. The classical and quantum fields exchange photons by means of the atoms. It is shown that under certain conditions this process is collective. The number of photons in a quantized mode oscillates, and the amplitude of these oscillations is proportional to N ². The frequency of the oscillations is determined by the frequencies of the classical and external fields.