Continuous optical generation of microwave signals for fountain clocks

Abstract

For the optical generation of ultrastable microwave signals for fountain clocks we developed a setup, which is based on a cavity stabilized laser and a commercial frequency comb. The robust system, in operation since 2020, is locked to a 100 MHz output frequency of a hydrogen maser and provides an ultrastable 9.6 GHz signal for the interrogation of atoms in two caesium fountain clocks, acting as primary frequency standards. Measurements reveal that the system provides a phase noise level which enables quantum projection noise limited fountain frequency instabilities at the low $10^{-14}(\tau /\mathrm{s}{)}^{-1/2}$ level. At the same time it offers largely maintenance-free operation.

8 pages, 4 figures

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• Frequency ratio of two optical clock transitions in ${}^{171}$Yb${}^{+}$ and constraints on the time-variation of fundamental constants
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Cited by in corpus (1)

• Characterization of Long-Term Stable Photonic Microwaves based on a Difference Frequency Comb