Magnetic particle detection using a uniformly polarized four-channel SERF atomic magnetometer

The SERF atomic magnetometer's remarkable sensitivity to low-frequency weak magnetic fields, combined with the high transmission of magnetic fields through biological tissues, makes it a promising technology for biomedical detection applications. In this study, we propose a uniformly polarized four-channel magnetometer with a diffractive optical element (DOE) and successfully apply it to detect the magnetic field signals of moving magnetic particles in a fluid. First, a method that accelerates polarization measurements using simultaneous four-channel responses is implemented. Furthermore, a result is obtained showing that the polarization gradients caused by light absorption are compensated by nearly 50 % using the reflection configuration. The more uniform polarization distribution contributes to the highly consistent responses, achieving sensitivities better than 5 fT/Hz^1/2 and bandwidths of 40 Hz. Additionally, we apply this four-channel magnetometer to detect magnetic particles in fluids. Using wavelet transform and weighted centroid algorithm to locate the signal moments, the velocity of particles is obtained, and a linear relationship between the flow rate and the velocity is established. This compact and sensitive scheme provides a valuable and noninvasive approach for various clinical applications involving magnetic particles, such as hemodynamics monitoring in cardiovascular disease, and concentration quantification in drug delivery.