Theoretical and experimental investigation of the light shift in Ramsey coherent population trapping

The ac Stark shift (or light shift) of the 62S1/2(F=3↔4) transition in 133Cs, as observed through coherent population trapping under pulsed excitation, is measured using a 133Cs gas cell and the D1-line vertical-cavity surface-emitting laser. This light shift can be calculated using density-matrix analysis. We derive an expression for this shift as a function of light intensity, showing that it varies linearly with respect to light intensity only with intensities higher than 1.0 mW/cm2. For pulsed excitation of high laser intensity, the variation in light shift is 20 times lower than that when using a continuous wave. The differences between the results of theory and experiment are discussed, taking into account the difference in conditions assumed; the results from theoretical analysis, taking the attenuation of the first-order sideband into account, approximately agree with the experimental results. The light shift is reduced by shortening the observation times. © 2014 American Physical Society.

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Author Yuichiro Yano Family Medicine and Community Health