All-optical magnetometric sensor for magnetoencephalography and ultralow field tomography

A version of the scheme of an atomic cesium vapour magnetometric sensor using magnetic resonance excitation by modulated radiation transverse to the magnetic field of hyperfine optical pumping is proposed and experimentally studied. It is shown that when using a cell with a volume of 0.125 cm$^3$, the variational sensitivity of the sensor, estimated from the ratio of the steepness of the signal at the center of the magnetic resonance to the shot noise of the detecting radiation, reaches a level of less than 10 fT/Hz$^{1/2}$ in the frequency band determined by the magnetic resonance line width (of the order of 800 Hz). The sensor, which does not use and does not emit resonant radio-frequency fields, is designed to operate in magnetoencephalographic complexes. Possible ways to increase the frequency response of the circuit for detecting relatively fast ($\sim$4.2 kHz in a field of 0.1 mT) proton magnetic moment precession signals in promising ultralow field tomography schemes are considered.