Investigation of the frequency characteristics of a ring laser by the method of small perturbations

Experimental results are presented concerning the influence of the parameters of an He-Ne ring laser (lambda = 0.63 micron) on the beat frequency between counterpropagating waves during laser-frequency tuning with respect to the gain line profile. The beat-frequency deviation signal is converted by a frequency detector to a signal with a perturbation frequency whose amplitude depends on the magnitude of the perturbation. It is shown that, in order to reduce the beat-frequency deviation to 0.1 per sec, it is necessary that the lasing-frequency instability not exceed 2 x 10 to the -9th, that the current instability in the discharge channel not exceed 0.006, and that the unbalance of currents in the discharge channels not exceed 0.1 mA.