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URSI International Symposium on Electromagnetic Theory

Study of field misalignment in a cavity used for atomic clock applications

Anton E. Ivanov, C. Affolderbach, G. Mileti, Anja K. Skrivervik

Published Aug 1, 2016• 1 citation
Publisher

Abstract

In vapor cell atomic clocks the atom-field interaction is typically obtained inside a microwave cavity resonator in which the microwave driving field together with a static magnetic field and an optical field are applied to excite the atoms. These fields are generally well-controlled, mutually aligned to a common quantization axis. Since the exploited atomic transition is sensitive to any potential axis misalignment, the performance of the clock can also be affected. We study the effect of such misalignment for the case of a cylindrical cavity used in vapor-cell atomic clocks, taking into account the misalignments of the optical detection field and the static magnetic field required for the atomic transition. Both the geometry of the cavity and the factors contributing to losses can play role in the degradation of the signal and are taken into account in the misalignment problem discussed.

DOI
10.1109/ursi-emts.2016.7571382

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Vapor-cell devices based on microwave interrogation provide a stable frequency reference with a compact and robust setup. Further miniaturization must focus on optimizing the physics package, containing the microwave cavity and atomic reservoir. In this article, we present a compact cavity-cell assembly based on a dielectric-loaded cylindrical resonator. The loaded cavity resonating at 6.83 GHz has an external volume of only 35 cm3and accommodates a vapor cell with 0.9-cm3inner volume. The proposed design aims at strongly reducing the core of the atomic clock, maintaining, at the same time, high-performing short-term stability (σy(τ)≤5×10−13 τ−1/2\sigma _{y}{(}\tau {)} \leq {5}\times {10}^{-{13}} \,\tau ^{-{1}/{2}}σy​(τ)≤5×10−13τ−1/2 standard Allan deviation). The proposed structure is characterized in terms of microwave field uniformity and atom-field coupling with the aid of finite-element calculations. The thermal sensitivity is also analyzed and experimentally characterized. We present preliminary spectroscopy results by integrating the compact cavity within a rubidium clock setup based on the pulsed optically pumping technique. The obtained clock signals are compatible with the targeted performances. The loaded-cavity approach is, thus, a viable design option for miniaturized microwave clocks.
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