High-Sensitivity Operation of Unshielded Radio Frequency Atomic Magnetometers Using Phase-Lock Techniques

High-sensitivity operation of radio frequency atomic magnetometers (AMs) in unshielded environment requires compensation of low-frequency fluctuations of the ambient magnetic field. Here, we demonstrate the use of phase-lock (PL) techniques to stabilize the magnetic environment and achieve high sensitivity at high frequencies. This is achieved by using the output of the AM both for stabilization and for measurement purposes. The approach is validated by a proof-of-concept in unshielded environment. The PL approach is also compared to the standard approach, where the magnetic environment is stabilized with the help of a set of fluxgate magnetometers, and it is shown that the PL approach features superior performances in signal detection.