Increase in the frequency stability and reproducibility of He–Ne standards utilizing the E component of methane

A master frequency-measuring system is described in which one of the laser standards is used as a frequency standard and the other as a reference. Typical operating features and the principal characteristics of each of the lasers are discussed. In the case of the frequency reference, a frequency shot-to-shot reproducibility of the order of 10^–15 is reported for short time intervals. The achieved frequency stability of the frequency standard oscillator is 10^–14 over 1–2 h.