Development of an optical time scale

A time standard based on the use of an optical oscillation period of a frequencystable He−Ne laser as a time scale is first described. We obtained highly frequency-stable oscillations in the SHF range that were locked to the oscillations of a He−Ne laser stabilized to an absorption resonance in methane at 3.39 μm. A direct comparison of frequency stabilities of a rubidium standard and He−Ne/CH4 laser has been made. The absolute measurement of the frequency of the He−Ne/CH4 laser we performed gave a new value of frequency.