Two-dimensional biaxial magnetic field imaging with millisecond resolution

Abstract

Multi-axial dynamic magnetic field imaging with femto-Tesla sensitivity paves a promising route for acquiring comprehensive information of the extremely-weak magnetic source. Here we propose a two-dimensional (2D) scanning imaging configuration that can realize rapid biaxial magnetic field measurement. Based on the Bragg diffraction, the configuration utilizes two orthogonally-arranged acousto-optic modulators to scan the probe laser temporally and spatially, realizing a 2D (7 × 7 pixels) magnetic field detection. To solve the multi-axial dynamic magnetic field imaging problem, a non-modulated time-sharing technique is theoretically and experimentally verified. Profiting from the non-modulated biaxial working mode that avoids long demodulation time, the magnetometer realizes millisecond temporal resolution (17.15 ms) for each sensitive axis. Operation in the spin-exchange relaxation-free regime, the single-pixel measurement sensitivity reaches around 2.6 fT/Hz1/2 (y-axis) and 7.5 fT/Hz1/2 (z-axis). Furthermore, weak pump and probe lasers power (500 μW and 350 μW) make it a low-power imaging device.