The passive optically pumped Rb frequency standard: the laser approach

Jaques Vanier, M. W. Levine, D. Janssen +1 more

The paper summarizes the relative advantages and disadvantages of coherent population trapping (CPT) or intensity optical pumping (IOP) for the implementation of a passive atomic frequency standard using the isotope /sup 87/Rb. This paper outlines the basic principles common to both CPT and IOP when using laser optical pumping, and makes explicit their similarities and their differences. This paper describes experimental results obtained in the same cell on the characteristics of the CPT and IOP /sup 87/Rb-hyperfine-resonance line. The measurements showed that the signal contrast is larger in CPT than in IOP for the same resulting line width; the light shift is smaller in CPT than in IOP, and is easier to control; in principle, a passive frequency standard based on CPT has a smaller size than that based on IOP, due to the absence of a microwave cavity. Conclusions on overall expectations for the future of such frequency standards are drawn.

W.A. Stern, Robert Novick

Zhangyou Du

Jaques Vanier, C. Mandache

This paper provides an overview of the efforts accomplished during the last few decades in the attempt of implementing a Rb-cell frequency standard using optical-microwave double resonance and laser optical pumping. The results of a new analysis based on a three-level model are summarized. Pumping rates, line widths, light shifts, cell radiation transmission and resonance signal size relative to background are calculated making use of the coherence property of the pumping laser. The expected frequency stability is calculated. The results obtained by several research groups are reviewed, compared to the analysis, and evaluated in the context of the implementation of a practical frequency standard. It is concluded that compromises must be made between the goal of obtaining a frequency stability close to the shot noise limit and that of minimizing complexity. Two directions that address such compromises are outlined.

Jianliao Deng, Zhengfeng Hu, Lin Li +1 more

C. Affolderbach, G. Mileti, Fabien Droz

A laser optically-pumped vapour-cell atomic frequency standard ("Rb clock") using a DFB laser diode as pump light source is presented. The Rb clock is based on probing the ground-state hyperfine "clock" transition at 6.8 GHz of atomic87Rb, by optical-microwave double-resonance technique. The frequency stability of the clock is measured.