We present a method for measuring the magnetic field that allows hyperfine and Zeeman optical pumping, excitation and detection of magnetic resonance by means of a single laser beam with time-modulated ellipticity. This improvement allows us to significantly simplify the Bell-Bloom magnetometric scheme, while retaining its sensitivity. The method does not require the use of radio-frequency fields, which is essential when creating arrays of sensors. The results of experimental studies demonstrate the efficiency of the proposed method and its potential applicability in most challenging magnetoencephalographic tasks.

Magnetic sensors developed for application in magnetoencephalography must meet a number of requirements; the main ones are compactness, sensitivity and response speed. We present a quantum optically pumped atomic sensor with cell volume of 0.5 cm ³ that meets these requirements and is operable in nonzero magnetic fields. The ultimate sensitivity of the sensor was estimated as (using the criteria of the ratio of the slope of the magnetic resonance signal to the shot noise spectral density) to be better than 5 fT/ √Hz. The actual sensitivity, measured in a gradiometric scheme, reaches 13 fT/ √Hz per sensor. We also present a novel and fast algorithm for optimization of the geometric properties of non-zero field sensor array with respect to maximization of the information transfer rate for cortical sources.

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

Silicon photodiodes have been tested for resistance to vacuum-ultraviolet radiation at 121.6 nm. The responsivities of the p- n and n- pphotodiodes under study were found to degrade by tens of...