Properties of Rb CPT Atomic Clock at Subharmonic Microwave Modulation Frequencies

Daba Radnatarov,Sergey Kobtsev,Arkadii Yakovlev,Sergey Khripunov,Valerii Andryushkov,Evgenii Baklanov

doi:10.1109/jphot.2019.2925012

Daba Radnatarov, Sergey Kobtsev + Show 4 more

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https://doi.org/10.1109/jphot.2019.2925012

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Abstract

This letter presents for the first time a systematic study of an atomic frequency standard based on сoherent population trapping (CPT) effect in 87Rb vapour optically pumped with a multifrequency laser radiation formed with sidebands of a single-frequency laser whose injection current is modulated at a subharmonic frequency (1/2–1/6) relative to the frequency of hyperfine ground state splitting. Measured are the CPT resonance parameters and the atomic clock short-term stability at different subharmonic frequencies of microwave modulation. The possibility of CPT resonance light shift suppression is experimentally demonstrated at modulation frequencies between 1/3 and 1/5 of the resonant frequency for continuous wave optical pumping of the 87Rb vapour D1 line. Analyzed are the capabilities and potential of reduced energy consumption of atomic clocks when CPT resonance in rubidium vapour is excited at subharmonic modulation frequencies.

Highlights

Coherent population trapping (CPT) effect [1] is widely used in miniaturised high-precision devices, such as atomic clocks [2], [3] and magnetometers [4], [5]
This letter presents for the first time a systematic study of an atomic frequency standard based on сoherent population trapping (CPT) effect in 87Rb vapour optically pumped with a multifrequency laser radiation formed with sidebands of a single-frequency laser whose injection current is modulated at a subharmonic frequency (1/2–1/6) relative to the frequency of hyperfine ground state splitting
CPT resonance is formed on hyperfine transitions of the ground state in an alkali atom exposed to bichromatic field created by microwave modulation of the injection current of a vertical-cavity surface-emitting laser (VCSEL) radiating at a frequency close to that of the ground state transition

Summary

Introduction

Coherent population trapping (CPT) effect [1] is widely used in miniaturised high-precision devices, such as atomic clocks [2], [3] and magnetometers [4], [5]. Compact dimensions of equipment based on the CPT effect enables its application in navigation, telecommunication, geo-location, and geodesy. Miniaturisation of CPT-based technology poses new, more stringent requirements to energy consumption and prompts various efforts to reduce it. CPT resonance is formed on hyperfine transitions of the ground state in an alkali atom exposed to bichromatic field created by microwave modulation of the injection current of a vertical-cavity surface-emitting laser (VCSEL) radiating at a frequency close to that of the ground state transition. Energy consumption of the microwave components responsible for generation of the necessary optical sidebands may exceed 50% of the. Total energy budget of CPT atomic clock [6], [7]. Optimisation of the microwave circuit in such devices is very promising in this respect

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