Optical Pumping Method to Reduce Light Shift in a Vapor Cell Atomic Frequency Standard

A novel optical pumping method is developed to reduce the light shift (AC Stark shift) in a vapor cell atomic frequency standard. The method uses the multiple excited state energy levels to cancel the total light shift. The collision-broadened linewidth in the optical transition is used to reduce the resultant influence of the laser frequency detuning. Experimentally, the laser beam polarization is used to reduce the intensity variation induced clock frequency shift while the buffer gas pressure is adjusted to reduce the laser frequency fluctuation induced clock frequency shift.