Femtotesla all-optical dual-axis spin-exchange relaxation-free magnetometer

The sensitivity of existing all-optical atomic magnetometers is significantly compromised due to the simultaneous influence of optical parameters on both optical pumping and optical modulation of atoms. The tight interlinkage of these processes poses challenges for their individual optimization, thereby restricting the achievable sensitivity. To address this issue, we developed a comprehensive optical modulation analytical model that fully considers the effects of dynamic optical pumping. Building upon this model, we introduced a multi-objective optimization method for optical parameters, leading to minimal non-sensitive axis crosstalk and optimal sensitivity. Experimental results demonstrated a femtotesla all-optical spin-exchange relaxation-free magnetometer with sensitivities of 2 fT/Hz1/2 along the y-axis and 4 fT/Hz1/2 along the x-axis, respectively. This advancement surpasses the sensitivity of existing optically modulated magnetometers and bears profound implications for the advancement and application of arrayed magnetometers.