A New Method to Suppress the AC-Stark Shift of Compact Cesium Beam Atomic Clocks

Abstract

Cesium beam atomic clocks are widely used as frequency standards in time-keeping, communication, navigation and positioning as primary frequency standards. Compared to cesium beam clocks with magnetic state selection, optical pumping clocks have several advantages like high utilization rate of cesium atoms, no Majorana transition, etc. However, they have an obvious drawback, the AC Stark effect, or the so-called light shift. In order to solve this problem, this paper presents a new method to suppress the light shift in cesium beam clocks. The clock used in experiment uses the optically detected magnetic-state-selection scheme. We demonstrate theoretically that the α and β coefficients can be strongly suppressed by introducing the detuned light into the detection light. In addition, we experiment this scheme and the α-coefficient is successfully reduced from 1.23E−12/mW to 8E−14/mW. We also test the long term frequency stability with additional laser intensity noise. It’s shown that the Allan deviation at 20000s is reduced from 2.0E−13 to 5.9E−14, which reveals the suppression of the light shift with our method. Although the scheme proposed in this paper is based on optically detected magnetic-state-selection scheme, this method can be easily applied to compact optical pumping Cs clocks. These results are relevant for improving the long-term frequency stability of compact cesium beam atomic clocks.