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Atomic-Signal-Based Zero-Field Finding Technique for Unshielded Atomic Vector Magnetometer

We describe a novel technique that can find the zero field in Earth's magnetic field for unshielded laser-pumped atomic magnetometer using atomic signal itself. By comparing light intensity of the pumping beam through atomic vapor cell under different magnetic fields, it decides which direction to move the compensation magnetic field and whether to increase or decrease the magnitude of increments in the compensating field. A convergence criterion is proposed, which not only keeps the field around zero, but also gives the precision of the compensation. The zero field is found in less than 23 s and the field increment after converging is smaller than 0.01, 0.01, and 0.04 μT for the x, y, and z axes, respectively, limited by 50-Hz noise in the laboratory environment. This method uses only one laser beam, which facilitates its application in chip-scale devices.