Collapse of laser action because of energy distribution in a resonator. Emission from a ruby laser with a moving selector

A theoretical analysis is made of the stimulated emission from a laser with plane external mirrors in the case of strong modulation of the threshold due to a redistribution of the energy in the resonator. It is shown that a monotonic displacement of internal dielectric boundaries gives rise to a periodic collapse of the laser action in each mode and to multirnode emission. In real lasers such displacements may be due to heating of the active medium, its vibrations, etc. All these factors affect the spectral kinetics under free-oscillation conditions. The influence of the redistribution of the energy on the laser emission is compared with the experimental results obtained for a ruby laser.