A Miniaturized Spin‐Exchange Relaxation‐Free Atomic Magnetometer Array Based on a 1 × 8 Planar Lightwave Circuit Waveguide Splitter

Abstract Using spin‐exchange relaxation‐free (SERF) atomic magnetometer array (AMA) in magnetocardiography and magnetoencephalography has presented a challenge in reducing its packing volume for integrated instrumentation and convenient maintenance. This study presents a novel, space‐saving SERF AMA based on an 8‐channel planar lightwave circuit (PLC) waveguide splitter with a compact footprint of 26 × 2.5 mm 2 . The PLC splitting configuration allows the synchronization of the pump for a multisensor array, resulting in highly consistent performance among the sensors, with an impressive ultrahigh sensitivity of 34 fT Hz −1/2 within a measurement bandwidth of 105 Hz. The PLC splitting method shows great promise in expanding the channel capacity of small‐scale SERF AMAs, offering a cost‐effective method for high‐resolution medical diagnoses through functional magnetic imaging of humans. In addition, this method is expected to find applications in fields such as electromagnetic induction imaging, biological magnetism, and geomagnetic observation.