Dual-Species All-Optical Magnetometer Based on a Cs-K Hybrid Vapor Cell

We build and characterize a dual-species all-optical magnetometer based on a Cs-K hybrid vapor cell with a paraffin coating. Using the amplitude-modulated Bell-Bloom scheme and Faraday-rotation measurement, we show that the spin polarization of Cs and K atoms can be generated and detected independently. The noise floor of the Cs channel is 35fT/Hz, whereas that of the K channel is 260fT/Hz, which is affected mainly by the magnetic resonance broadening in the presence of mutual spin-exchange collisions. With use of the proposed device, in situ magnetic field stabilization is realized by use of (i) the K channel to monitor and compensate for the magnetic field noise and (ii) the Cs channel to read out the magnetic field after active stabilization. The low-frequency magnetic field noise can be suppressed by a factor of more than 1000 in the presence of magnetic field gradients. When applied to magnetic field stabilization, such in situ measurement is achieved more compactly and is more accurate than ex situ measurement that is realized with two spatially separated vapor cells. In addition, the proposed scheme could also be applied in a practical ground-surveying magnetometer based on dual working species.