CALCIUM OPTICAL FREQUENCY STANDARD BASED ON ATOM INTERFEROMETRY

We report on an optical frequency standard utilizing the Ca intercombi nation line at lambda approximate to 657 nm as frequency reference. Th e discriminant signal used for the frequency stabilization is derived from high-resolution atom interferences generated by separated-field e xcitation of Ca atoms either in an effusive atomic beam or in a magnet ooptical trap. For the effusive beam, the realization uncertainty is a few parts in 10(12). It can be reduced below 10(-14) by cooling and t rapping of the atoms. The frequency of the Ca frequency standard was m easured in a phase-coherent frequency comparison with the primary stan dard of time and frequency, the Cs-atomic clock to be 455986240493.95 kHz with a relative standard uncertainty of < 10(-12).