Thermal and Magnetic Field Analysis of a Low- Interference Heating Coil for VCSEL-Based SERF Atomic Magnetometers

A low-magnetic-noise heating structure is proposed for temperature regulation of vertical-cavity surface-emitting lasers (VCSELs) used in miniaturized spin-exchange relaxationfree (SERF) atomic magnetometers. In compact SERF systems, the VCSEL package is usually positioned close to the alkali-metal vapor cell, and the current flowing through the temperaturecontrol structure can introduce residual magnetic fields and field gradients in the sensing region. To address this issue, a doublelayer 2N pole resistive heating coil is designed to replace the conventional thermoelectric-cooler-based temperature-control scheme. A three-dimensional multiphysics model is established in COMSOL Multiphysics to evaluate the magnetic-field suppression capability of the proposed coil and the thermal performance of different substrate materials. Compared with a conventional heating coil, the proposed structure substantially reduces the magnetic flux density under different observation distances and coil spacings. The extracted magnetic-field distribution inside the vapor-cell region remains on the order of 10-2 nT, and the field variation along the z-direction is below 0.006 nT. For a 3mm vapor-cell dimension, this corresponds to an equivalent field gradient below 2 nT/m, indicating weak magnetic perturbation in the sensing volume under the assumed simulation conditions. Thermal simulations further show that, under an input heating power of 0. 1 W, the aluminum nitride substrate provides better temperature uniformity than the aluminum oxide substrate, with the temperature difference reduced from approximately 0.37 °C to 0. 0 8° C. These results suggest that the proposed heating structure can simultaneously suppress current-induced magnetic interference and improve heat spreading, providing a simulationbased design basis for VCSEL integration in miniaturized SERF atomic magnetometers.