The ac Stark shift (or light shift) of the 6 2 S 1/2 (F = 3 ↔ 4) transition in 133 Cs, as observed through coherent population trapping under pulsed excitation, is measured using a 133 Cs gas cell and the D 1 -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/cm 2 . 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. * Electronic address: yano-yuichiro@ed.tmu.ac.jp

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This paper presents a theoretical and experimental investigation on the light shift (AC Stark shift) of the 6 2 S 1/2 (F = 3 ↔ 4) transition in 133 Cs, as observed through coherent population trapping (CPT) under a pulsed excitation. The calculated results are good agreement in the experimental results on various parameters and show that the light shift under pulsed excitation is 20∼30 times less than that under continuous excitation. In addition, this paper also presents a two-step pulse method for suppressing the light shift.