The Microloop-Gap Resonator: A Novel Miniaturized Microwave Cavity for Double-Resonance Rubidium Atomic Clocks

Abstract

Abstract-Nowadays mobile and battery-powered applications push the need for radically miniaturized and low-power frequency standards that surpass the stability achievable with quartz oscillators. For the miniaturization of double-resonance rubidium ( 87 Rb) atomic clocks, the size reduction of the microwave cavity or resonator (MWR) to well below the wavelength of the atomic transition (6.835 GHz for 87 Rb) is of high interest. Here, we present a novel miniaturized MWR, the μ-LGR, for use in a miniature DR atomic clock and designed to apply a well-defined microwave field to a microfabricated Rb cell that provides the reference signal for the clock. This μ-LGR consists of a loop-gap resonator-based cavity with very compact dimensions (<0.9 cm 3 ). The μ-LGR meets the requirements of the application and its fabrication and assembly can be performed using repeatable and low-cost techniques. The concept of the proposed device was proven through simulations, and prototypes were successfully tested. Experimental spectroscopic evaluation shows that the μ-LGR is well-suited for use in an atomic clock. In particular, a clock short-term stability of 7 × 10 −12 τ −1/2 was measured, which is better than for other clocks using microfabricated cells and competitive with stabilities of compact Rb clocks using conventional glass-blown cells.

Chip-scale atomic devices

“…More recently, CPT has been used in vapor cell clocks, 36,37 including CPT masers. [38][39][40][41] Most chip-scale atomic clocks rely on coherent population trapping, although new miniature microwave cavities 42 remain a viable alternative for miniaturized atomic clocks. A review of the application of CPT to atomic clocks can be found in Ref.…”

Imaging Microwave and DC Magnetic Fields in a Vapor-Cell Rb Atomic Clock

“…G.-X. Du, T. Bandi, A. Horsley, P. Treutlein, and G. Mileti,3 The design and study of different types of microwave resonator cavities with well-defined field distributions have been addressed, e.g., for compact vapor cell atomic clocks [11] and H-masers [12], high-performance Rb clocks based on the continuous-wave (cw) [13], [14] or pulsed optical pumping (POP) approach [6,15], or miniaturized Rb clocks [16], [17]. In primary atomic fountain clocks, effects such as distributed phase shifts in the cavity can become relevant [18].…”

Technological Assessment of MEMS Alkali Vapor Cells for Atomic References

“…MEMS alkali vapor cell technology, utilizing eutectic bonding, has been investigated for years [65,66,67,68,69,70]. According to this technology, the silicon–glass preform and glass cover, kept at a distance, are located in the vacuum chamber.…”