Power resonances and frequency stabilization of a gas laser with a nonlinear-absorption cell

Power resonances in the emission of a gas laser are considered in the case of spectral hole burning (a laser with a Fabry–Perot resonator) and of interaction between the oscillation modes at frequencies close to the center of a gain or absorption line (a laser with a ring resonator). In the second case, the resonances may be much narrower and have a higher contrast than the resonances in the emission of a laser with a Fabry–Perot resonator. Stabilization is reported for a helium–neon laser with a Fabry–Perot resonator, emitting a peak associated with the saturation of the absorption in methane.