Condition for single-frequency emission from short gas lasers

A theoretical analysis is made of the condition for single-frequency stimulated emission at the center of a line of a gas laser with a short resonator. A calculation is given of the maximum length of the resonator in which interfering modes are still below the threshold. This calculation is carried out for a wide range of values of the pumping rate in excess of the threshold and for a wide range of ratios of the homogeneous and Doppler broadening. The results obtained may be useful in the design of lasers with interference-type mode selection.