Dick effect in a pulsed atomic clock using Coherent Population Trapping

Abstract

The Dick effect can be a limitation of the achievable frequency stability of a passive atomic frequency standard when the ancillary frequency source is only periodically sampled. Here we analyze the Dick effect for a pulsed vapor cell clock using coherent population trapping (CPT). Due to its specific interrogation process without atomic preparation nor detection outside of the Ramsey pulses, it exhibits an original shape of the sensitivity function to phase noise of the oscillator. Numerical calculations using a three-level atom model are successfully compared with measurements; an approximate formula of the sensitivity function is given as an easy-to-use tool. A comparison of our CPT clock sensitivity to phase noise with a clock of the same duty cycle using a two-level system reveals a higher sensitivity in the CPT case. The influence of a free-evolution time variation and of a detection duration lengthening on this sensitivity is studied. Finally this study permitted to choose an adapted quartz oscillator and allowed an improvement of the clock fractional frequency stability at the level of 3.2x10-13 at 1s

References in corpus (3)

• Metrological characterization of the pulsed Rb clock with optical detection
• Coherent Population Trapping Resonances in Buffer Gas-filled Cs Vapor Cells with Push-Pull Optical Pumping
• Ramsey spectroscopy of high-contrast CPT resonances with push-pull optical pumping in Cs vapor

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• Optimization of laser dynamics for active stabilization of DF--VECSELs dedicated to cesium CPT clocks
• Two-step pulse observation for Raman-Ramsey coherent population trapping atomic clocks