Robust calibration of vector optically pumped magnetometers (OPMs) is a; nontrivial task, but increasingly important for applications requiring; high-accuracy such as magnetic navigation, geophysics research, and; space exploration. Here, we showcase a vector OPM that utilizes Rabi; oscillations driven between the hyperfine manifolds of 87Rb to measure the direction of a DC; magnetic field against the polarization ellipse structure of a; microwave field. By relying solely on atomic; measurements—free-induction decay (FID) signals and Rabi measurements; across multiple atomic transitions—this sensor can detect drift in the; microwave vector reference and compensate for systematic shifts caused; by off-resonant driving, nonlinear Zeeman (NLZ) effects, and buffer; gas collisions. To facilitate deadzone-free operation, we also; introduce a Rabi measurement that utilizes dressed-state resonances; that appear during simultaneous Larmor precession and Rabi driving; (SPaR). These measurements, performed within a microfabricated vapor; cell platform, achieve an average vector accuracy of 0.46 mrad; and vector sensitivities down to 11µrad/Hz for geomagnetic field strengths near; 50 µT. This performance surpasses the challenging 1-deg; (17 mrad) accuracy threshold of several contemporary OPM; methods utilizing atomic vapors with an electromagnetic vector; reference.
