All-optical dual-axis zero-field atomic magnetometer using light-shift modulation

Functional imaging equipment based on miniaturized atomic magnetometers with array arrangement exhibits promising prospects in biomagnetic scenarios. However, crosstalk from the modulated magnetic field between adjacent sensors degrades the imaging accuracy. To address this issue, this study proposes an all-optical dual-axis zero-field atomic magnetometer using light-shift modulation. We utilize an acousto-optic modulator to modulate a detuned circularly polarized beam for pumping the atomic spin ensembles. This beam allows for the optical modulation of spin polarization and meanwhile generates a light-shift modulation, effectively replacing the conventional magnetic field modulation. By using a probe beam to detect the optical rotation angle perpendicular to the direction of the pump beam, we construct an all-optical configuration of a longitudinally modulated atomic magnetometer, enabling dual-axis magnetic field measurements. Experimental results demonstrate dual-axis sensitivities of 29 and $15\mathrm{fT}/{\mathrm{Hz}}^{1/2}$, respectively. This method eliminates the need for conventional coil-based magnetic field modulation, thereby paving the way for potential applications in magnetocardiography and magnetoencephalography.

Figure 1

Simulation results of the nonsensitive-axis crosstalk according to Eqs. (17) and (18) in (a) dc demodulation and (b) first-harmonic demodulation.

Figure 2

Schematic of the experimental setup. DFB, distributed feedback laser; DBR, distributed Bragg reflector laser; AOM, acousto-optic modulator; PMF, polarization-maintaining fiber; CL, collimator; LP, linear polarizer; QWP, quarter-wave plate; HWP, half-wave plate; PBS, polarization beam splitter; PD, photodiode; TIA, transimpedance amplifier; LIA, lock-in amplifier; FG, function generator; DAQ, data acquisition.

Figure 3

Comparison of the simulated and experimental nonsensitive-axis crosstalk in (a) dc demodulation and (b) first-harmonic demodulation for k = 5. The blue curves represent simulated nonsensitive-axis crosstalk, and the orange error bars depict experimentally measured nonsensitive-axis crosstalk.

Figure 4

Sensitivities of the all-optical dual-axis zero-field atomic magnetometer. The results include a calibration magnetic field with a frequency of 30.5 Hz, an amplitude of 10 pTrms, and an additional peak at 50 Hz introduced by industrial frequency interference.

Figure 5

Frequency response of the all-optical dual-axis zero-field atomic magnetometer. The solid lines (solid boxes) represent the results obtained from fitting (experimental) data.