Coherent population trapping for the realization of a small, stable, atomic clock

Abstract

The Coherent Population Trapping phenomenon (CPT) has created interesting avenues in the practical realization of atomic frequency standards using laser optical pumping. In practice two different types of standards can be implemented: a passive clock based on the dark state created in the ensemble by the CPT phenomenon and a maser based on the ground state oscillating magnetization induced by the same phenomenon. The paper describes the basic physics involved in the approach and summarizes the progress made up to now in the practical implementation of such frequency standards.

Atomic clocks based on coherent population trapping: basic theoretical models and frequency stability

“…CPT appears to offer substantial advantages relative to size over the classical intensity optical pumping technique (IOP). The matter has been discussed in some details in the case of the passive approach in which no microwave cavity is required leaving freedom in connection to the resonance cell design [15,16,17]. In the case of the maser approach, there is no oscillation threshold regarding cavity Q and radiation intensity [3].…”

Solid-state atomic frequency standard

“…However, the cost and power consumption of both technologies stands in the way of more widespread application of precision frequency control. Recent trends in frequency standards have been to aggressively shrink the size of rubidium atomic clocks and attempt to develop batch manufacturing techniques to lower the production cost [2,3,4,5,6,7,8,9,10,11,12]. For crystal oscillators, every possible refinement has been applied in the last few decades to improve the long-term accuracy and temperature stability [13,14,15,16,17,18], and to reduce the power consumption of oven-controlled devices [19,20,21,22,23].…”

“…Regardless of the implementation, the desired frequency is derived from the atomic spectrum of a gas of atoms or ions, rather than from the mechanical dimensions and mass of a piezoelectric resonator. Further details of conventional, miniature atomic clocks may be found in the following references [2][3][4][5][6][7][8][9][10][11][12].…”

“…Most recent miniaturized designs use coherent population trapping rather than the traditional optical pumping technique using a rubidium lamp and filter [6,7,8,9,11].…”

Component-level demonstration of a microfabricated atomic frequency reference

“…This work is a contribution of NIST, an agency of the US government, and is not subject to copyright. [30,31,[42][43][44][45][46][47]. Physics packages for compact frequency references based on CPT have also been developed [48] and the scaling of this type of frequency reference with cell size was investigated [1].…”