Analysis of the light shift effect in the Rb-87 frequency standard

The Rb-87 cell frequency standard, optically pumped by a laser diode, is of great interest in the development of high-stability, short-term oscillators, We report the experiments performed on a rubidium-cell prototype aiming to evaluate the transfer of the laser and microwave noise to the hyperfine clock transition via the light shift effect, which appears to be the main contribution to the observed short- and medium-term instabilities in this kind of a standard, Pulsed optical pumping is also examined in order to strongly reduce the light-shift effect: the experimental results show an improvement in medium term frequency stability.