Gas laser with nonlinear absorption under quasitraveling wave conditions

A gas laser with nonlinear absorption, operating under quasitraveling wave conditions, is considered theoretically in the case of strong saturation of the absorption. The output power increases resonantly and the emission frequency is pulled strongly toward the center of an absorption line when the field frequency passes through the center of such a line. It is shown that, in contrast to the standing-wave case, the generation of a quasitraveling wave in a resonator makes it possible to obtain high peak powers and to achieve large values of the self-stabilization factor even in the case of strong saturation of the absorption and considerable differences between the saturation parameters of the amplifying and the absorbing media. This makes it possible to achieve, in principle, the condition of absolute selfstabilization of the frequency when a nonlinear pulling of the frequency into a power peak is maintained, even though the resonator frequency is detuned by an amount equal to the interval between the axial modes of a Fabry–Perot resonator. The conditions for achieving such operation are found and an example of a CO₂ laser with an absorption cell filled with SF₆ is considered.