Chip-Scale Optically Pumped Magnetometry Enabled by Tailorable Elliptical Dichroism Metasurface

Emerging miniaturized optically pumped magnetometers (OPMs) are becoming one of the most desirable approaches for biomagnetic imaging, especially for OPM with elliptically polarized light, which promises single-light optical pumping and detection with high sensitivity. However, conventional schemes of this kind require a set of bulk polarization optics and tedious adjustment procedures, which compromise the system's compactness and practicality. In this paper, a novel chip-scale OPM scheme that leverages the monolithic elliptical meta-polarizer is presented and experimentally demonstrated. The meta-polarizer with a side length of 3 mm is laid out on a 2 × 2 cm² glass wafer. It offers the capability to convert arbitrary incident polarization into the desired elliptical polarization and exhibits a tailorable elliptical dichroism (ED) of ≈0.77 at the wavelength of 795 nm. A 4 × 4 × 4 mm³ vapor cell containing ⁸⁷Rb and N₂ is combined with this elliptical meta-polarizer to construct a miniaturized OPM. The sensitivity of this sensor reaches approximately 13 fT/Hz^1/2 in a four-layer magnetic shield with a dynamic range near zero magnetic field ≈ ±0.55 nT. By exploiting the advantages of planar integrated optics, reduced footprints and scalability are promised. And this work paves the way for the integration of emerging quantum sensors on a chip.