Spiral Radiator Chip for Rb and Xe Spin Polarization in Miniaturized NMR Co‐Magnetometers

ABSTRACT Nuclear magnetic resonance (NMR) co‐magnetometers are high‐precision atomic sensors, but their practical deployment is hindered by bulky free‐space optics. Here, we propose a circularly polarized light radiation scheme based on a silicon nitride photonic platform and develop a compact, chip‐scale integrated optical pumping module. Distinct from prior on‐chip schemes limited to electron spin polarization, our approach achieves polarization of alkali metal electron spins and noble gas nuclear spins. By integrating a spiral waveguide with angular gratings, the platform emits vertically propagating CPL with a 5.65° divergence angle, and the average degree of circular polarization exceeds 95%. Magnetic field‐dependent measurements reveal clear 129 Xe and 131 Xe precession responses. A 50% increase in SRC pumping power increases the relative nuclear spin polarization of 129 Xe by a factor of 1.72 and that of 131 Xe by a factor of 2.90, verifying efficient nuclear spin polarization. The SRC scheme yields electron and nuclear spin resonance responses in the vapor cell, while the SRC chip itself occupies a compact footprint of only 1 × 2 mm 2 . This work offers a highly integrated photonic solution for atomic polarization, facilitating the miniaturization and practical deployment of high‐performance NMR co‐magnetometers.