Compact and high-performance Rb clock based on pulsed optical pumping for industrial application

Abstract

We report on the development of a compact laserpumped Rb clock based on the pulsed optical pumping (POP) technique, in view of future industrial applications. The clock Physics Package (PP) is based on a compact magnetron-type microwave cavity of 45 cm 3 volume, and our current clock PP has a volume of only 0.8 liters, including temperature control and magnetic shields. This clock PP is completed by a newlydeveloped frequency-stabilized laser head of 2.5 liters overall volume, with an acoustic optical modulator (AOM) integrated within the laser head for switching the laser output power. Due to the highly uniform magnetic field inside the microwave cavity, Ramsey signals with high contrast of up to 35% and with a linewidth of 160 Hz have been demonstrated. A typical shortterm clock stability of 2.4×10 -13 τ -1/2 is measured. Thanks to the pulsed operation, the light-shift effect has been considerably suppressed as compared to previously demonstrated continuouswave (CW) clock operation using the same clock PP, which is expected to enable improved long-term clock stabilities down to the 10 -14 level or better.

Optically-detected spin-echo method for relaxation times measurements in a Rb atomic vapor

“…This is fundamentally different from the case of anti-relaxation wall-coated cells without buffer gas where the atoms move freely through the entire cell volume and experience only homogeneous shifts and broadenings as well as narrowing [43]. Figure 2 shows the schematics of our experimental setup, basically a Rb atomic clock, whose details were previously presented in [30,31]. It consists of three main parts: (1) the physics package containing the microwave cavity and the vapor cell, (2) the compact frequency-stabilized laser head (LH), and (3) the microwave synthesizer.…”

“…This method is a combination of Franzen [12], Ramsey-DR [16] and NMR spin-echo [21] techniques. We apply the ODSE method to our high-performance 87 Rb atomic frequencystandard setup presented in [30,31] and show how to determine the intrinsic coherence relaxation time (T 2 ) specifically for the 'clock transition'…”

“…In section 2 we briefly recall the theory of relaxation processes in a buffer-gas vapor cell [3], and use it to estimate the 'intrinsic' population and coherence relaxation times (T 1 and T 2 respectively) of the clock transition in our 87 Rb vapor cell. In section 3, we introduce the experimental setup which is basically a Rb atomic clock [30,31]. Finally in section 4, we present the results of relaxation times measured in the same 87 Rb vapor cell by using ODSE, Franzen, continuous-wave double-resonance (CW-DR), and Ramsey-DR methods.…”

Compact clocks for industrial applications: The EMRP project IND 55 MClocks

“…In these experiments clear Ramsey fringes on the clock signal were obtained, showing a fringe contrast of 35% at a central fringe width of 160 Hz, and resulting in a short-term clock stability of 2.1x10 -13 τ -1/2 [9]. The frequency-stabilized laser system including an acoustooptical modulator (AOM) for switching the optical output has also been developed and realized (optics assembly volume of 1 liter only) and was used successfully to operate a POP clock [10]. These new building blocks will contribute to achieve a very compact clock physics package, in view of a clock realization for industrial applications.…”

Study of additive manufactured microwave cavities for pulsed optically pumped atomic clock applications

“…1). The openings at both ends of the cavity allow the laser light, provided by a compact laser head emitting at 780 nm (Rb D2 line), 19 to travel through the cell, with k also parallel to the symmetry axis z. For all measurements presented here, the laser frequency was stabilized to the F g ¼ 2 $ F e ¼ 3 Doppler-free resonance obtained from an auxiliary evacuated Rb vapor cell integrated in the laser head.…”