Optical Parameter Decoupling and Optimization for Elliptically Polarized Atomic Magnetometer

— Elliptically polarized atomic magnetometers (AMs) offer high sensitivity and compactness by using a single laser beam to polarize atoms and detect optical rotation angles. However, their sensitivity advantage over optical absorption-based AMs has not been sufficiently demonstrated. This is because the optical parameters significantly affect the pumping and probing processes, leading to parameter coupling when both processes are optimized simultaneously. Such coupling presents a considerable challenge for achieving simultaneous parameter optimization, ultimately limiting the achievable sensitivity. In this study, we developed a modified input–output model for a magnetometer, based on which an optical parameter decoupling and optimization method is proposed. Our method enables us to obtain the optimal optical parameters simultaneously, including the ellipticity, intensity, and frequency of light. Consequently, a sensitivity of 6 fT/Hz^1/2 was achieved using a 4 × 4 × 4 mm^{3 87}Rb vapor cell (an effective volume of 0.027 cm³). This work offers an efficient strategy to achieve higher sensitivity using single-beam miniaturized AMs, contributing significantly to promote biomagnetism research.