Reproducibility of the frequency of a quantum reference source stabilized by the $E$ component of the methane molecule

An experimental study was made of the reproducibility of the frequency of an He–Ne laser stabilized by the $E$ component of the $\nu_3[P(7)]$ transition in the methane molecule. The frequency of the output radiation was influenced by the principal parameters and the operating conditions of the laser, including its output power, methane pressure, detuning of the gain line relative to the absorption of methane, and amplitude of the frequency deviation of the laser radiation. It was found that the laser frequency depended strongly on the degree of stopping down of the laser beam by the amplifying tube. The reproducibility of the laser radiation frequency achieved in these experiments was $5\cdot10^{-13}$. An estimate was obtained of the maximum precision of the frequency reproducibility of an unperturbed transition in this type of laser.