High-Quality Atom-Manipulation by Pancharatnam-Berry Metasurface for High-Sensitivity Miniaturized Optically Pumped Magnetometers

Precise atom-manipulation by light plays a pivotal role in optically pumped magnetometers (OPMs), involving the fundamental interaction between light and atoms, as it significantly enhances the sensitivity and stability of magnetic field measurements. However, the available laser beams matched with a vapor of alkali metal atoms (such as rubidium or cesium) cannot simultaneously provide a perfect circularly polarized state and the desired profile (Gaussian beam), which are essential conditions for polarizing alkali metal atoms used in OPMs. Currently, the conventional approaches adopt a complex optical system involving beam shapers (i.e., spatial light modulators), waveplates, and additional functional lenses, which bring limitations of bulkiness, complex adjustments, and high cost in OPMs. Here, we report a new high-quality atom-manipulation approach using an angular-tilted Pancharatnam-Berry (PB) metasurface for high-sensitivity miniaturized OPMs. By precisely engineering the nanostructures of each amorphous silicon meta-atom, the metasurface is capable of efficiently converting incident light at a specific wavelength (770 nm) into a desired circularly polarized state with a predetermined deflection angle. Simultaneously, it has the ability to shape the wavefront to generate an ideal Gaussian profile, accurately achieving atom spin polarization for high-sensitivity miniaturized X-ray-guided OPMs. The deflection angle can efficiently eliminate zero-level noise and achieve full conversion. We experimentally found that the angular-tilted PB metasurface-based OPM with a potassium small vapor cell can implement a sensitivity lower than 400 fT/Hz^1/2, which is higher performance than conventional optical methods. This approach provides a new perspective for miniaturized OPMs to precisely measure the magnetic field in various applications.