Magnetic-field-insensitive coherent-population-trapping resonances excited by bichromatic linearly polarized fields on the $D_1$ line of $^{133}$Cs

TL;DR

This paper demonstrates magnetic-field-insensitive CPT resonances in $^{133}$Cs using lin || lin polarized light on the $D_1$ line, showing potential for highly stable miniature atomic clocks.

Contribution

It introduces a simple lin || lin excitation scheme for CPT resonances with minimal magnetic sensitivity, suitable for compact atomic clock applications.

Findings

Resonance frequency shift is only 0.04 Hz at 1 μT deviation.

CPT amplitude increases with excitation intensity and matches a three-level model.

Resonance stability surpasses conventional clock transitions.

Abstract

We have experimentally demonstrated that magnetic-field-insensitive coherent-population-trapping (CPT) resonances are generated between the ground hyperfine levels on the $D_1$ line of $^{133}$Cs using a two-photon $\Lambda$ scheme excited by lin || lin polarizations. The frequency shift of the CPT resonance is 0.04 Hz for the deviation of 1 $\mu$T at a "magic" magnetic field of 139 $\mu$T and is 50 times smaller than that of the conventional clock transition at a typical bias magnetic field for the clock operation. The amplitude of the CPT spectrum excited by lin || lin polarizations is enhanced as the excitation intensity increases and is well explained by the three-level model without trap levels. Thus, the CPT resonance on the $D_1$ line of $^{133}$Cs atom excited by a simple lin || lin scheme will be one of the best candidates for frequency reference of miniature atomic clocks.