Optimization of bandwidth and signal responses of optically pumped atomic magnetometers for biomagnetic applications

Recently developed ultrasensitive optically pumped atomic magnetometers are promising for biomagnetic measurements such as magnetoencephalograms and magnetocardiograms. The magnetometer's bandwidth and amplitude of signal response are important factors for biomagnetic measurements. These factors depend on various operating parameters such as power density and wavelengths of laser beams. By focusing on the transverse spin relaxation time, we theoretically and experimentally studied the change in the bandwidth and amplitude of the signal response. By considering the effect of the attenuation of a pump beam inside a cell, we showed good agreement between theoretical and experimental results. Furthermore, the magnetometer's integrated performances for the factors were evaluated by changing the power density of the pump beam. Measured data indicated that the bandwidth of signal response depended on the power density of the pump beam and that the bandwidth could be tuned to a desirable frequency range.