3.10-12. τ- 12 / On industrial prototype optically pumped cesium beam frequency standard

The GALILEO European global Positioning program requires very stable clocks either for space or ground applications. This paper describes the short-term stability improvement study on an industrial prototype developed by TEKELEC SYSTEMES. This study has been performed with the scientific support from SYRTE and the financial support from DGA/CELAR. The prototype is designed to reach one of the industrial goals: small sized sealed tube and compact optical bench rigidly fixed along it. In this paper we focus on the optical device using two laser wavelengths in order to improve the clock frequency stability: the 4-4 pumping transition of the cesium D₂ line for the atomic preparation and the 4-5 cycling transition for the atomic detection. The experimental results reported in this paper show that the atomic detection with an optical cycling transition improves the frequency stability by a factor 3 to 6 compared to the basic scheme using the same optical pumping transition for both preparation and detection purposes. This high performance level is reached with a low atomic flux consistent with a ten-year lifetime and a commercial DBR diode laser having a spectral linewidth as high as 3 MHz.