Estimation of a Light Shift Using Various Atomic Resonances in Ramsey-Coherent Population Trapping Sequence

This study aimed to detect the light shift by utilizing various atomic resonances observed under pulsed excitation with drive current modulation (DCM). Light shift degrades the performance of atomic clocks, and several studies have attempted to mitigate or correct it. Pulsed excitation with DCM facilitates the observation of various Ramsey-coherent population trapping (CPT) resonances owing to wavelength variation. Further, in the Ramsey-CPT sequence, a semi-continuous wave CPT resonance (SCW-CPT resonance), which is a continuous wave CPT resonance from pulsed lasers, is also observed. As these atomic resonances exhibit different frequency sensitivities to laser intensity, the frequency shifts differ based on the changes in laser intensity. This facilitates the detection of the light shift. By simultaneously measuring the resonance frequencies of two Ramsey-CPT resonances and the SCW-CPT resonance while varying the laser intensity to induce light shifts, we measured the resulting frequency changes. Each resonance exhibited a different frequency shift in response to the light shift. Therefore, this study conformed the feasibility of detecting and estimating the light shift in an operational atomic clock.