Transportable optical frequency standard and results of its metrological tests

The first compact He–Ne laser (λ = 3.39 μ ) stabilized using the resolved central component of the magnetic hyperfine structure of the F₂⁽²⁾ line of methane was constructed. The frequency stability of this laser was 2×10^–14 (τ = 100 sec) and the reproducibility was ~10^–13. The natural frequency of this component on a scale set by the primary Cs frequency standard was determined with the highest currently attainable precision (~10^–12).