Optically pumped magnetometers based on symmetric frequency-detuning modulated light

The elliptically polarized optically pumped magnetometer (OPM) employs a single-beam of off-resonant elliptically polarized light to measure magnetic fields by detecting optical rotation angles, offering advantages of compactness and high sensitivity. However, the used off-resonant light introduces the AC-Stark shift. It perturbs the atomic Zeeman levels and can be comparable to a non-uniform fictitious magnetic field, degrading the response and introducing relaxation. In this study, we develop symmetric frequency-detuning modulated light to pump OPMs, which achieves rapid switching between symmetric red and blue detuning. Driven by it, the AC-Stark field rapidly reverses its direction and thus the average effect of the three-dimensional AC-Stark field is nullified. Meanwhile, the optical rotation angle is modulated optically, enhancing the response signal in the detection process. Finally, under the frequency-detuning of about 90 GHz, an average AC-Stark field of approximately 9.5 nT was unsensitized and a 70 % improvement in sensitivity was achieved in elliptically polarized OPMs. Our approach facilitates the applications of highly sensitive OPMs in biomagnetism measurements and frontier physics research.