Realization of a pulsed optically pumped Rb clock with a frequency stability below $$10^{-15}$$

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 $$1.2\times 10^{-13}$$ 1.2 × 10 - 13 at 1s and achieves the value of $$6\times 10^{-16}$$ 6 × 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.