A pulsed optically pumped Rb clock with a frequency stability below 10-15

TL;DR

This paper reports a vapor cell Rb clock using pulsed optical pumping achieving record frequency stability below 10^-15, suitable for space applications, through precise stabilization of pulses.

Contribution

It demonstrates a space-qualified pulsed optically pumped Rb clock with unprecedented stability, combining engineered physics package and laboratory-grade optics.

Findings

Frequency stability of 1.2×10^-13 at 1 s

Achieves 6×10^-16 at 40000 s

Requires careful stabilization of microwave and laser pulses

Abstract

We present the frequency stability performances of a vapor cell Rb clock based on the pulsed optically pumping (POP) technique. The clock has been developed in the frame of a collaboration between INRIM and Leonardo SpA, aiming to realize a space-qualified POP frequency standard. The results here reported were obtained with an engineered physics package, specifically designed for space applications, joint to laboratory-grade optics and electronics. The measured frequency stability expressed in terms of Allan deviation is $1.2 \times 10^{-13}$ at 1 s and achieves the value of $6 \times 10^{-16}$ for integration times of 40000 s (drift removed). This is, to our knowledge, a record result for a vapor-cell frequency standard. In the paper, we show that in order to get this result, a careful stabilization of microwave and laser pulses is required.