In situ measurement of magneto-optical non-orthogonality in miniaturized atomic magnetometer

Miniaturized atomic magnetometers (M-AMs) are important tools for bio-magnetic measurements, but their performance is limited by magneto-optic non-orthogonality (MON). In this study, a response signal model considering MON is established, and an in situ measurement method combining this model and the magneto optical relationship is proposed. Considering this, the MON of five M-AMs are measured. We found that MON over 1 degrees is common. The measurement results verify the accuracy of the principle derived from the model. Compared with only compensating the residual magnetism and after additional compensation of the light shift caused by MON, the M-AM calibration coefficient with large MON improves by 44.6%, and the sensitivity increases from 25.29 to 16.25 fT/Hz1/2 (@31.5 Hz). The calibration coefficient with small MON improves by 10%, and the sensitivity increases from 14.10 to 12.15 fT/Hz1/2 (@31.5Hz). With a minimum bandwidth of 140 Hz, it fully satisfies the requirements of the magnetometer. This study completed the in situ measurement of MON without auxiliary equipment, which can be easily applied to other multi-axis vector magnetometers. The measurement and evaluation of MON is crucial for the efficient operation and pursuit of higher sensitivity magnetometers.