STRONG MODE COUPLING INDUCED IN A GAS LASER BY AN INTRACAVITY SATURABLE ABSORBING MEDIUM

Abstract
Although gas lasers generally operate in the weak mode‐coupling regime, one may induce strong coupling, hence single‐moding, by means of a saturable absorbing medium placed within the resonator. The effect occurs under conditions where, although the linear gain of the amplifier cell may exceed the linear loss of the absorption cell, the absorber may saturate more heavily than the amplifier. The analysis, based on the coupled energy‐balance equations, indicates that the power in the surviving mode may be considerably enhanced.