Study of additive manufactured microwave cavities for pulsed optically pumped atomic clock applications
Applied Physics Letters, American Institute of Physics, 2018/112//113502/1-5
Additive manufacturing (AM) of passive microwave components is of high interest for the cost-effective and rapid prototyping or manufacture of devices with complex geometries. Here, we pre-sent an experimental study on the properties of recently demonstrated microwave resonator cavities manufactured by AM, in view of their applications to high-performance compact atomic clocks. The microwave cavities employ a loop-gap geometry using six electrodes. The critical electrode structures were manufactured monolithically using two different approaches: Stereolithography (SLA) of a polymer followed by metal coating and Selective Laser Melting (SLM) of aluminum. The tested microwave cavities show the desired TE<sub>011</sub>-like resonant mode at the Rb clock frequency of ≈6.835 GHz, with a microwave magnetic ﬁeld highly parallel to the quantization axis across the vapor cell. When operated in an atomic clock setup, the measured atomic Rabi oscillations are com-parable to those observed for conventionally manufactured cavities and indicate a good uniformity of the ﬁeld amplitude across the vapor cell. Employing a time-domain Ramsey scheme on one of the SLA cavities, high-contrast (34%) Ramsey fringes are observed for the Rb clock transition, along with a narrow (166 Hz linewidth) central fringe. The measured clock stability of 2.2 × 10<sup>-13</sup> <i>τ</i><sup>-1/2</sup> up to the integration time of 30 s is comparable to the current state-of-the-art stabilities of com-pact vapor-cell clocks based on conventional microwave cavities and thus demonstrates the feasibility of the approach.
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