# A high-performance Raman-Ramsey Cs vapor cell atomic clock

## TL;DR

This paper presents a high-performance Cs vapor cell atomic clock using pulsed CPT with push-pull optical pumping, achieving excellent short-term stability and reduced laser power sensitivity, suitable for advanced technological applications.

## Contribution

The study introduces a pulsed CPT Cs atomic clock with push-pull optical pumping that enhances stability and reduces laser power sensitivity compared to continuous regimes.

## Key findings

- Achieved a fractional frequency stability of 2.3×10⁻¹³ at 100 seconds.
- Found that the pulsed regime narrows the Ramsey fringe line-width.
- Demonstrated reduced laser power sensitivity in the pulsed CPT clock.

## Abstract

We demonstrate a high-performance coherent-population-trapping (CPT) Cs vapor cell atomic clock using the push-pull optical pumping technique (PPOP) in the pulsed regime, allowing the detection of high-contrast and narrow Ramsey-CPT fringes. The impact of several experimental parameters onto the clock resonance and short-term fractional frequency stability, including the laser power, the cell temperature and the Ramsey sequence parameters, has been investigated. We observe and explain the existence of a slight dependence on laser power of the central Ramsey-CPT fringe line-width in the pulsed regime. We report also that the central fringe line-width is commonly narrower than the expected Ramsey line-width given by $1/(2T_R)$, with $T_R$ the free-evolution time, for short values of $T_R$. The clock demonstrates a short-term fractional frequency stability at the level of $2.3 \times 10^{-13}~\tau^{-1/2}$ up to 100 seconds averaging time, mainly limited by the laser AM noise. Comparable performances are obtained in the conventional continuous (CW) regime, if use of an additional laser power stabilization setup. The pulsed interaction allows to reduce significantly the clock frequency sensitivity to laser power variations, especially for high values of $T_R$. This pulsed CPT clock, ranking among the best microwave vapor cell atomic frequency standards, could find applications in telecommunication, instrumentation, defense or satellite-based navigation systems.