Phase and light shift determination in an optically pumped cesium beam frequency standard

Area of Science:

• Atomic physics
• Metrology
• Optical physics

Background:

• Optically pumped Cesium (Cs) beam frequency standards are essential for precise timekeeping.
• Accurate determination of phase and light shifts is critical for minimizing uncertainty in these standards.
• Existing methods may be susceptible to errors if light shift effects are not properly addressed.

Purpose of the Study:

• To investigate the impact of light shift on phase shift determination in optically pumped Cs beams.
• To demonstrate the necessity of correcting for light shift in fitting procedures.
• To improve the accuracy and reduce uncertainty in Cs beam frequency standards.

Main Methods:

• Utilizing an optically pumped Cs beam apparatus.
• Employing a fitting method to determine phase difference without beam reversal.
• Comparing results obtained with and without correction for light shift.

Main Results:

• An uncorrected light shift can induce errors in phase difference measurements.
• Correcting experimental data for light shift brings fitting method results into agreement with beam reversal results.
• The uncertainty in the accuracy budget of the Cs standard was reduced.

Conclusions:

• Accurate determination of phase shift in optically pumped Cs beams requires accounting for light shift.
• Correction for light shift enhances the reliability of fitting methods.
• The improved method leads to a state-of-the-art frequency standard accuracy of 6.3x10⁻¹⁵.