Metrological characterization of the pulsed Rb clock with optical detection

Abstract

We report on the implementation and the metrological characterization of a vapor-cell Rb frequency standard working in pulsed regime. The three main parts that compose the clock, physics package, optics and electronics, are described in detail in the paper. The prototype is designed and optimized to detect the clock transition in the optical domain. Specifically, the reference atomic transition, excited with a Ramsey scheme, is detected by observing the interference pattern on a laser absorption signal.The metrological analysis includes the observation and characterization of the clock signal and the measurement of frequency stability and drift. In terms of Allan deviation, the measured frequency stability results as low as 1.7 × 10 −13 τ −1/2 , τ being the averaging time, and reaches the value of few units of 10 −15 for τ = 10 4 s, an unprecedent achievement for a vapor cell clock. We discuss in the paper the physical effects leading to this result with particular care to laser and microwave noises transferred to the clock signal. The frequency drift, probably related to the temperature, stays below 10 −14 per day, and no evidence of flicker floor is observed.We also mention some possible improvements that in principle would lead to a clock stability below the 10 −13 level at 1 s and to a drift of few units of 10 −15 per day.1

Pulsed Optically Pumped Rb clock

“…The experimental set-up is represented in figure 1 and is composed of three parts: physics package, optics and electronics. A detailed description of the prototype can be found in [2]. Figure 1.…”

“…/day were obtained with this prototype [2]. Aiming to a further improvement of the clock performances, a new system is being developed taking in particular care the design of the microwave synthesis chain, the thermal stability and uniformity of the Rb cell.…”

Stability of a trapped-atom clock on a chip

“…This rivals trapped ion clocks, the best of which has shown 65 s interrogation time and a stability of 2 10 −14 at 1 s [14,15]. It is to be compared to compact clocks using thermal vapour and buffer gas [16][17][18] or laser cooled atoms [19][20][21][22]. Among these the * Peter.Rosenbusch@obspm.fr record stability is 1.6 × 10 −13 at 1 s [17].…”

“…It is to be compared to compact clocks using thermal vapour and buffer gas [16][17][18] or laser cooled atoms [19][20][21][22]. Among these the * Peter.Rosenbusch@obspm.fr record stability is 1.6 × 10 −13 at 1 s [17]. Clocks with neutral atoms trapped in an optical lattice have reached impressive stabilities down to the 10 −18 range [23,24] but their interrogation time is so far limited by the local oscillator.…”

Scheme for a compact cold-atom clock based on diffuse laser cooling in a cylindrical cavity

“…Laser pumped Rubidium vapor cell clock has been demonstrated with the replacement of the lamp by a compact frequency-stabilized laser [1]. Godone et al developed a clock scheme called pulsed optically-pumped (POP) in a vapor-cell which uses a diode laser for the optical pumping and the Ramsey technique to interrogate atoms [2][3][4]. In this scheme, the light shift can be greatly reduced.…”