Mitigation of the magnetic-field-induced frequency shift in coherent-population-trapping atomic clocks

Abstract

We study the magnetic-field-induced frequency shift (MFS) of the reference resonance in a coherent population trapping (CPT) microwave atomic clock. It is shown that the use of the Pound–Drever–Hall-like technique for frequency locking provides brilliant opportunities for mitigating the MFS. Using a 0.125 cm3 rubidium vapor cell with a buffer gas, we have measured a residual sensitivity of the reference CPT resonance frequency to be ≈70μHz/mG over ≈6 mG interval. It means that a fractional frequency shift is extremely small (≈1×10−14 mG−1). The results contribute to the development of a new-generation CPT-based miniature atomic clock with improved long-term frequency stability. The proposed method is sufficiently versatile and can be adapted for other excitation schemes in atomic clocks, including those based on Ramsey-like or double-resonance techniques.