Long-Term Stability Analysis Toward -14 Level for a Highly Compact POP Rb Cell Atomic Clock

Area of Science:

• Atomic Physics
• Metrology
• Quantum Technologies

Background:

• Long-term frequency instabilities in vapor-cell clocks are mainly due to environmental and experimental parameter fluctuations.
• These fluctuations are converted into clock frequency shifts through various physical processes.
• Understanding these sensitivities is crucial for developing stable atomic clocks.

Purpose of the Study:

• To analyze frequency sensitivities and stability limitations of a rubidium vapor-cell clock.
• To investigate a compact magnetron-type cavity clock operated in ambient air.
• To establish a long-term instability budget for the clock under stable pressure conditions.

Main Methods:

• Operated a rubidium vapor-cell clock with a magnetron-type cavity in ambient air.
• Measured frequency sensitivities and instability at a one-day timescale.
• Established a long-term instability budget, measuring parameter fluctuations via atomic response where possible.

Main Results:

• Atmospheric pressure fluctuations can significantly limit clock stability via the barometric effect under ambient conditions.
• The measured clock instability at one day was limited by the intensity light-shift effect.
• Identified potential for improvement through active laser intensity stabilization or enhanced optical pumping.

Conclusions:

• The study provides a comprehensive instability budget for the rubidium vapor-cell clock.
• Achieving excellent long-term stabilities (≤ 10⁻¹⁴ at one day) is feasible for simple, compact, low-power vapor-cell clocks in ambient conditions.
• Further improvements can be made by addressing laser intensity fluctuations and optimizing optical pumping.