Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)

Estimation of the light shift in Ramsey-coherent population trapping

Yuichiro Yano, Shigeyoshi Goka, Masatoshi Kajita

Published Apr 1, 2015• 5 citations
Publisher

Abstract

We both numerically and analytically investigate on the light shift in Ramsey-CPT resonance for compact atomic clocks. The numerical calculation of the light shift is based on a density matrix analysis in Λ-type three state model. And the analytical method leads to an estimation equation of light shift in the Raman-Ramsey scheme. The estimation equation expresses the relationship between light shift and all pulse parameters. The results show that the estimation equation was reproduced well as the numerical results.

DOI
10.1109/fcs.2015.7138814

Related papers

Investigation on light shift in CPT-Ramsey resonance for compact atomic clocks

Yuichiro Yano, Wujie Gao, Shigeyoshi Goka +1 more

This paper presents a theoretical and experimental investigation on the light shift (AC Stark shift) of the 62S1/2(F = 3 ↔ 4) transition in133Cs, 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.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)•May 1, 2014•0 citations

Two-step pulse observation for Raman–Ramsey coherent population trapping atomic clocks

Yuichiro Yano, Shigeyoshi Goka, Masatoshi Kajita

We propose a two-step pulse observation method to enhance the frequency stability of coherent population trapping (CPT) atomic clocks. The proposed method is a Raman–Ramsey scheme with low light intensity at resonance observation and provides a Ramsey-CPT resonance with both reduced frequency sensitivity to the light intensity and a high signal-to-noise ratio by reducing the repumping into a steady dark state. The resonance characteristics were calculated using density matrix analysis of a Λ-type three-level system that was modeled on the 133 Cs D 1 line, and the characteristics were also measured using a vertical-cavity surface-emitting laser and a Cs vapor cell.

arXiv:1411.3779•Applied Physics Express•Dec 11, 2014•8 citations

Light-shift comparison of electromagnetically induced transparency and coherent population trapping in continuous-wave and Ramsey spectroscopies

Xiaoyan Liu, Xu Zhao, Zhen Xu +1 more

In the atomic frequency standard, the light shift inevitably affects the long-term stability of the atomic clock. In this work, we accurately calculated the light shifts of electromagnetically induced transparency (EIT) and coherent population trapping (CPT) clocks operating under continuum and pulse sequence regimes by numerically solving the Liouville density matrix equation, including all the relaxation terms of a three-level system. The results show that the light shifts under pulse excitation are smaller than those under continuous excitation and the light shifts of the CPT process are much smaller than those of the EIT process under both excitations. It is also found that the light shifts in the continuous excitation increase and those in the pulse excitation decrease with an increase in the Rabi frequency. The light shifts will increase with an increase of the relaxations of the ground states for both the processes under both regimes. Compared to all process atomic clocks, the light shift of pulse-excited atomic clocks is the smallest, which will be suitable for many applications.

Journal of the Optical Society of America B•Mar 2, 2021•2 citations

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

Masahiro Fukuoka, Sigeyoshi Goka

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.

IEEE Ultrasonics, Ferroelectrics, and Frequency Control Joint Symposium (UFFC-JS)•Sep 22, 2024•0 citations

Light shift of Ramsey coherent population trapping resonance using drive current modulation

Masahiro Fukuoka, Shigeyoshi Goka, Masatoshi Kajita +1 more

Abstract We investigated the light shift of Ramsey coherent population trapping (CPT) resonance by drive current modulation (DCM), which can be realized with low power consumption in a small system, to improve the performance of a CPT atomic clock. The light shift makes the greatest contribution to the degradation of long-term frequency stability of a CPT atomic clock. We also devised digitizer-based DCM to reduce the uncertainty in the frequency of light shift due to wavelength variation at the time of observation. The results show that light shift with DCM is reduced compared with cw excitation and is consistent with theoretical calculations. The estimated frequency uncertainty of the light shift due to wavelength variation using the proposed method is 2.1 × 10−13, which is approximately 165 times better than that of the conventional method without a digitizer, thus demonstrating the effectiveness of the proposed method for future small atomic clocks.

Japanese Journal of Applied Physics•Nov 16, 2023•5 citations

Computational studies of light shift in a Raman–Ramsey interference-based atomic clock

G. S. Pati, Zachary Warren, Nan Yu +1 more

Determining light shift in Raman–Ramsey (RR) interference is important for the development of atomic frequency standards based on a vapor cell. We have accurately calculated light shift in RR interference using the density-matrix equations for a three-level system without invoking the adiabatic approximation. Specifically, phase shifts associated with coherent density-matrix terms are studied as they are relevant to the detection of RR interference in transmission (or absorption) through the medium. For the single-velocity case, the numerically computed results are compared with the analytical results obtained using the adiabatic approximation. The result shows light shift suppression in conformity with the closed-form analytic solutions. The computational studies have also been extended to investigate RR interference for a Doppler-broadened vapor medium. Importantly, a velocity-induced frequency shift is found at the fringe center as an additional source of frequency error for a vapor cell Raman clock.

arXiv:1411.5292•Journal of the Optical Society of America B•Feb 3, 2015•31 citations
We both numerically and analytically investigate on the light shift in Ramsey-CPT resonance for compact atomic clocks. The numerical calculation of the light shift is based on a density matrix analysis in Λ-type three state model. And the analytical method leads to an estimation equation of light shift in the Raman-Ramsey scheme. The estimation equation expresses the relationship between light shift and all pulse parameters. The results show that the estimation equation was reproduced well as the numerical results.
This paper presents a theoretical and experimental investigation on the light shift (AC Stark shift) of the 62S1/2(F = 3 ↔ 4) transition in133Cs, 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.
We propose a two-step pulse observation method to enhance the frequency stability of coherent population trapping (CPT) atomic clocks. The proposed method is a Raman–Ramsey scheme with low light intensity at resonance observation and provides a Ramsey-CPT resonance with both reduced frequency sensitivity to the light intensity and a high signal-to-noise ratio by reducing the repumping into a steady dark state. The resonance characteristics were calculated using density matrix analysis of a Λ-type three-level system that was modeled on the 133 Cs D 1 line, and the characteristics were also measured using a vertical-cavity surface-emitting laser and a Cs vapor cell.
In the atomic frequency standard, the light shift inevitably affects the long-term stability of the atomic clock. In this work, we accurately calculated the light shifts of electromagnetically induced transparency (EIT) and coherent population trapping (CPT) clocks operating under continuum and pulse sequence regimes by numerically solving the Liouville density matrix equation, including all the relaxation terms of a three-level system. The results show that the light shifts under pulse excitation are smaller than those under continuous excitation and the light shifts of the CPT process are much smaller than those of the EIT process under both excitations. It is also found that the light shifts in the continuous excitation increase and those in the pulse excitation decrease with an increase in the Rabi frequency. The light shifts will increase with an increase of the relaxations of the ground states for both the processes under both regimes. Compared to all process atomic clocks, the light shift of pulse-excited atomic clocks is the smallest, which will be suitable for many applications.
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.
Abstract We investigated the light shift of Ramsey coherent population trapping (CPT) resonance by drive current modulation (DCM), which can be realized with low power consumption in a small system, to improve the performance of a CPT atomic clock. The light shift makes the greatest contribution to the degradation of long-term frequency stability of a CPT atomic clock. We also devised digitizer-based DCM to reduce the uncertainty in the frequency of light shift due to wavelength variation at the time of observation. The results show that light shift with DCM is reduced compared with cw excitation and is consistent with theoretical calculations. The estimated frequency uncertainty of the light shift due to wavelength variation using the proposed method is 2.1 × 10−13, which is approximately 165 times better than that of the conventional method without a digitizer, thus demonstrating the effectiveness of the proposed method for future small atomic clocks.
Determining light shift in Raman–Ramsey (RR) interference is important for the development of atomic frequency standards based on a vapor cell. We have accurately calculated light shift in RR interference using the density-matrix equations for a three-level system without invoking the adiabatic approximation. Specifically, phase shifts associated with coherent density-matrix terms are studied as they are relevant to the detection of RR interference in transmission (or absorption) through the medium. For the single-velocity case, the numerically computed results are compared with the analytical results obtained using the adiabatic approximation. The result shows light shift suppression in conformity with the closed-form analytic solutions. The computational studies have also been extended to investigate RR interference for a Doppler-broadened vapor medium. Importantly, a velocity-induced frequency shift is found at the fringe center as an additional source of frequency error for a vapor cell Raman clock.