Multifunctional Metafiber for Pumping SERF Atomic Magnetometer

Miniaturized spin-exchange relaxation-free (SERF) atomic magnetometer is an ultra-sensitive device for biomagnetic dynamic measurements, yet it still remains challenging in realizing easy-to-align and compact optical configuration while maintaining high sensitivity. In this study, we demonstrate a multi-functional metafiber, consisting of a compact metalens assembled on the facet of an optical fiber, for flexible and high-performance pump light delivery and manipulation in atomic magnetometers for the first time. By tailoring transmission and phase profiles of nanopillars, the metafiber simultaneously enables broadband collimation and polarization manipulation from 770 to 894 nm, a spectrum regime that covers most commonly used alkali metals in quantum technologies. We integrate the metafiber with a SERF atomic magnetometer and achieve magnetic field measurement with a sensitivity of 51.12 fTHz^−1/2 (@31.5 Hz). Beyond optically interfaced quantum systems, the demonstrated highly compact and easy-to-align multifunctional metafiber can also find widespread classical applications such as wavelength-multiplexing fiber-optic communications, fiber sensing and fiber lasers.