All-Optical Nonzero-Field Vector Magnetic Sensor for Magnetoencephalography

We present the concept and results of an investigation all-optical vector-magnetic-field sensor scheme developed for biological applications such as nonzero-field magnetoencephalography magnetocardiography. The differs from classical two-beam Bell-Bloom in that detecting laser beam is split into two beams, which are introduced cell orthogonal directions, ratio amplitudes magnetic resonance signals these beams their phase difference measured; strong optical pumping lower hyperfine level ground state ensures line narrowing, detection carried out balanced schemes by measuring beam-polarization rotation. proposed compact, resistant to variations parameters radiation highly sensitive angle deflection field vector---with estimated scalar sensitivity order $16\phantom{\rule{0.2em}{0ex}}{\mathrm{fT}/\mathrm{Hz}}^{1/2}$ $8\ifmmode\times\else\texttimes\fi{}8\ifmmode\times\else\texttimes\fi{}8\phantom{\rule{0.2em}{0ex}}{\mathrm{mm}}^{3}$ cell, angular $4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ rad, or 0.08'', was demonstrated.