ON PULSATING RADIATION IN WEAKLY INVERTED MEDIA

A change in the character of maser generation in a two-level system is found when the initial population inversion exceeds some threshold value equal to the square root of the total number of atoms. Above this threshold, the number of photons begins to grow exponentially with time and the pulse with short leading edge and broadened trailing edge is generated. In this work, we attempt to explain the nature of this threshold. Coherent pulse duration, estimated by its half-width, increases significantly with increasing inversion, if all other parameters are fixed and the absorption is neglected. The inclusion of the energy loss of photons leads to the fact that the duration of coherent pulse is almost constant with increasing inversion, at least well away from the threshold. If there is a mechanism for restoring population inversion, a pulsating regime for generating stimulated emission becomes possible. The integral radiation intensity at this can be increased several times. This approach can be used to analyze cosmic radiation, which could help explain the great diversity of pulsating radiation sources in space.