ELIMINATION OF THE LIGHT SHIFT IN RUBIDIUM GAS CELL FREQUENCY STANDARDS USING PULSED OPTICAL PUMPING

Thomas C. English, Ernst Jechart, T.M. Kwon

Abstract:	It is well known that changes in the intensity of the light source in an optically pumped, rubidium, gas cell frequency standard can produce corresponding frequency shifts, with possible adverse effects on the long-term frequency stability. Since this so-called "light-shift" effect is due to the simultaneous presence of pumping light and interrogating microwave ram diation, it can be eliminated, in principle, by alternately pulsing the pumping light and the microwave radiation so that there is no temporal overlap. We have constructed a pulsed optical pumping apparatus with the intent of investigating the frequency stability in the absence of light shifts. Contrary to our original expectations, a small residual frequency shift due to changes in light intensity has been experimentally observed. Evidenco is given which indicates that this is not a true light-shift effect. Preliminary measurements of the frequency stability of this apparatus, with this small residual "pseudo" light shift present, are presented. It is shown that this pseudo light shift can be eliminated by using a more homogeneous C-field. This is consistent with the idea that the pseudo light shift is due to inhomogeneity in the physics package ("position-shift" effect).
Published in:	Proceedings of the 10th Annual Precise Time and Time Interval Systems and Applications Meeting November 28 - 30, 1978 Goddard Space Flight Center Greenbelt, Maryland
Pages:	147 - 168
Cite this article:	English, Thomas C., Jechart, Ernst, Kwon, T.M., "ELIMINATION OF THE LIGHT SHIFT IN RUBIDIUM GAS CELL FREQUENCY STANDARDS USING PULSED OPTICAL PUMPING," Proceedings of the 10th Annual Precise Time and Time Interval Systems and Applications Meeting, Greenbelt, Maryland, November 1978, pp. 147-168.
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