Geometric phase metasurface-based circularly polarized light emitter for optical pumping of chip-scale atomic magnetometer

Atomic magnetometers (AMs) are among the most sensitive sensors for detecting magnetic fields. Achieving atomic spin polarization using circularly polarized light (CPL) near-resonant with the D1 transition of alkali atoms is fundamental to optical pumping-based magnetic field measurement. However, conventional optically pumped magnetometers rely on bulky optical pumping setups for atomic polarization, presenting significant challenges for portable and compact biomagnetic sensing applications. Here, we propose a compact and integrable on-chip optical pumping scheme employing an all-dielectric, waveguide-driven metasurface CPL emitter. The metasurface comprises 17 × 81 identical meta-atoms occupying an on-chip footprint of only 6μm×28μm. By precisely adjusting the rotation angles of the individual meta-atoms, we achieved uniform amplitude extraction of guided waves. Three-dimensional simulations predict a radiation efficiency of around 31 %, and experimental measurements verify that the emitted beam exhibits a degree of circular polarization (DoCP) of ∼ 0.71. As a proof-of-concept demonstration, we simulate the three-dimensional distribution of electron spin polarization (ESP) within an alkali vapor cell by the emitted beam, confirming the effectiveness of polarization. This approach significantly reduces the size of optical pumping equipment and simplifies optical alignment. Furthermore, it is fully compatible with complementary metal–oxide–semiconductor (CMOS) fabrication processes, offering the prospect of future integration with on-chip light source.