Contrast power resonances of a helium-neon laser with an absorption cell

A method for strongly enhancing the contrast of the power peaks of a laser with a nonlinear absorption cell was proposed and tested experimentally. The experiments were carried out on a helium–neon laser emitting 3.39 μ radiation and a methane absorption cell. The effectiveness of the method was due to the strong interaction of closely spaced modes in a homogeneously broadened line. The peak amplitudes achieved in this way and the considerable narrowing of these peaks should make it possible to increase considerably the long-term stability of the gas lasers.