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Updated: May 9, 2026
06:42
Generation and Coherent Control of Pulsed Quantum Frequency Combs
Published on: June 8, 2018
Active compensation of the AC Stark shift in a two-photon rubidium optical frequency reference using power modulation
Yorick Andeweg1,2, John Kitching1, Matthew T Hummon1
1National Institute of Standards and Technology, Boulder, Colorado, United States.
Physical Review Applied
|May 8, 2026
Summary
We developed a feedback protocol to reduce AC Stark shift in a rubidium optical frequency reference. This significantly improves clock stability, achieving 3 × 10-14 at 1s and 2 × 10-14 at 104s.
Area of Science:
- Atomic, Molecular, and Optical Physics
- Metrology and Measurement Science
- Quantum Information Science
Background:
- The AC Stark shift is a major limitation in optical atomic clocks, affecting both short-term and long-term stability.
- Rubidium-based optical frequency standards are crucial for precise timekeeping and fundamental physics research.
- Existing methods struggle to simultaneously optimize short-term and long-term clock stability due to the AC Stark shift.
Purpose of the Study:
- To implement a feedback protocol for suppressing the AC Stark shift in a two-photon rubidium optical frequency reference.
- To reduce the sensitivity of the frequency reference to optical power fluctuations.
- To investigate the impact of local oscillator frequency noise on clock stability when using this feedback method.
Main Methods:
- A feedback control loop was designed and implemented to actively counteract the AC Stark shift.
- The two-photon transition in a rubidium optical frequency reference was utilized.
- Experimental measurements were performed to quantify the reduction in optical power sensitivity and assess clock instabilities.
Main Results:
- The AC Stark shift's sensitivity to optical power variations was reduced by a factor of 1000.
- Simultaneous clock instabilities of 3 × 10-14 at 1 second and 2 × 10-14 at 104 seconds were achieved.
- A quantitative description and experimental exploration of the stability limit imposed by local oscillator frequency noise were provided.
Conclusions:
- The developed feedback protocol effectively suppresses the AC Stark shift, overcoming a key limitation in optical frequency standards.
- This method enables unprecedented simultaneous short-term and long-term stability in rubidium-based optical clocks.
- Understanding and mitigating local oscillator frequency noise is critical for reaching the ultimate stability limits of such clocks.
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