Method and apparatus for compensating a reference frequency shift

An apparatus for compensating a reference frequency shift due to an interaction of laser light provided by a resonant light source with atoms of an atomic beam crossing a resonant microwave cavity between light interaction zones, said apparatus comprising:

• a modulation unit adapted to toggle a wavelength of the provided light between a main optical pumping transition, OPT1, and an alternate optical pumping transition, OPT2, of the atoms of the atomic beam while a frequency of the microwave probe signal fed into the microwave cavity is modulated with a frequency modulation depth, FMD;
• a measurement unit adapted to measure signal amplitudes of produced Ramsey fringes;
• and
• a calculation unit adapted to compute a wavelength modulation compensation error signal, WM-CES, depending on the measured signal amplitudes of the produced Ramsey fringes used to control the frequency of the microwave probe signal fed into the microwave cavity of the apparatus.

An atomic clock device comprising an apparatus for compensating a reference frequency shift due to an interaction of light provided by a resonant light source with atoms of an atomic beam crossing a resonant microwave cavity between light interaction zones, said apparatus comprising:

• a modulation unit adapted to toggle a wavelength of the provided light between a main optical pumping transition, OPT1, and an alternate optical pumping transition, OPT2, of the atoms of the atomic beam while a frequency of the microwave probe signal fed into the microwave cavity is modulated with a frequency modulation depth, FMD;
• a measurement unit adapted to measure signal amplitudes of produced Ramsey fringes;
• and
• a calculation unit adapted to compute a wavelength modulation compensation error signal, WM-CES, depending on the measured signal amplitudes of the produced Ramsey fringes used to control the frequency of the microwave probe signal fed into the microwave cavity of the apparatus.