Analyze and customize modulation amplitude for multi-channel optically pumped magnetometers

Modulation amplitude, as a pivotal factor of optically pumped magnetometers (OPMs) in parametric modulation mode, is directly related to the response and sensitivity of OPMs. Due to variations in OPM parameters, there is no one-size-fits-all modulation amplitude for achieving optimal response in a multi-channel OPM system. In this study, we additionally consider the effect of modulation relaxation on OPM performance and develop a modified modulation amplitude-responsivity model. We also propose a multi-channel automatic modulation amplitude optimization method by searching for the maximum response based on the model. Our method efficiently obtains the customized optimal modulation amplitude for each OPM in an 8-channel OPM system with a planar layout. In this way, the system responsivity is enhanced by an average of 22.6% and the sensitivity is improved by more than 17.9%, compared to using an identical amplitude for all OPMs. This automatic method provides an efficient strategy to improve the performance of arrayed OPMs and brings prospective improvement to reveal more detailed signals in biomagnetic measurements utilizing multi-channel OPM-based magnetocardiography (OPM-MCG) systems.