Single-Beam Atomic Magnetometer Based on the Transverse Magnetic-Modulation or DC-Offset

We constructed a compact single-beam atomic magnetometer operated in a transverse magnetic-modulation mode or a DC-offset mode. By coupling the laser beam into a polarization maintaining fiber, with a vapor cell of the dimensions 4 mm $\times4$ mm $\times4$ mm, a sensitivity of 30 fT/Hz(1/2) has been achieved in the single-beam configuration. In addition to the experimental study of the sensitivity, we perform a theoretical analysis of the single-beam atomic magnetometer in the transverse magnetic-modulation mode and the DC-offset mode. The results indicate both of two modes have almost the same scale factor. We also studied the dynamic working range of the sensor and found, experimentally, that our sensor reaches a dynamic response range of +/- 3 nT, with a nonlinear error of 1%. The frequency responses of the transverse magnetic-modulation mode and the DC-offset mode are 125 Hz and 65 Hz, respectively. This sensor will be particularly suitable for applications that require high sensitivity, low cost and compact size, e.g., magnetoencephalography (MEG) and magnetocardiography (MCG).