Influence of backscattering on the operation of a ring laser with a methane cell

The influence of backscattering (reflection) on the position of the extremum of a "competing" methane peak in a λ = 3.39 μ ring laser was investigated experimentally and theoretically (a number of simplifying assumptions were made in the latter case). The experimental results indicated the possibility of a shift of this extremum by 300–300 Hz when the change due to backscattering by defects in optical elements was close to the internal phase shift.