Scalar Potassium Magnetometer Based On Amplitude Modulated Nonlinear Magneto-Optical Rotation

In this work, a scalar potassium magnetometer based on amplitude modulated nonlinear magneto-optical rotation (AM NMOR) is experimentally built and reaches noise level of $30{\text{fT}}/\sqrt {{\text{Hz}}} $ under a low-noise bias magnetic field. Our potassium magnetometer could be applied to a large earth’s magnetic field, where the performance of cesium magnetometer is limited by nonlinear Zeeman effect (NLZ). A group of totally separated magnetic-resonance lines are got and each line has a FWHW (full width half maximum) of ~10 Hz , which is 10-times narrower than cesium’s magnetic-resonance linewidth in the same case. The noise-level of $130{\text{fT}}/\sqrt {{\text{Hz}}} $ is achieved under bias magnetic field of 100000 nT, which is mainly due to ambient magnetic-field noise.