I. Introduction

Magnetoencephalography (MEG) is a noninvasive functional neuroimaging technique that uses magnetometers with high sensitivity across multiple channels to record the magnetic field generated by the brain’s naturally occurring electrical currents, thereby enabling the mapping of brain activities [1], [2]. Presently, superconducting quantum interference device (SQUID) arrays serve as the predominant magnetometers, while investigating the potential of optically pumped magnetometers (OPMs) operating in the spin-exchange relaxation-free (SERF) regime for future applications [3], [4]. Despite their high sensitivity, SQUIDs require liquid helium for cooling, which demands them to be contained within a Dewar bottle. Furthermore, the presence of a 15-mm liquid helium Dewar vacuum gap imposes limitations on the sensitivity and resolution of commercially available SQUID recordings of brain activity [5], [6]. With the rapid development of SERF technology over the past decade, OPM has emerged as a highly promising alternative to SQUIDs for MEG [7], [8]. Romalis et al. [9] initially proposed a highly sensitive alkali-metal atomic magnetometer based on the SERF regime, achieving a measurement sensitivity of by 2003 [10]. In contrast to SQUIDs, the OPM operates at temperatures ranging from 140 °C to 160 °C, eliminating the need for bulky cooling units [11], [12]. Furthermore, they can be positioned in closer proximity to the scalp. Therefore, OPM offers not only a notable reduction in maintenance costs but also a decrease in the distance between the sensor and the magnetic source in the brain, resulting in increased signal strength. This is attributed to the inverse square relationship between the amplitude of the magnetic field and the distance [13].