Chip-Scale Single-Beam Atomic Magnetometer Enabled by Spin-Selective Interference Meta-Optics

Emerging atomic magnetometers (AMs) are among the most advanced sensors for detecting and characterizing magnetic fields. Recently, there has been growing interest in the miniaturization and integration of AMs due to the urgent demand for portability and compactness in various fields such as biomagnetism imaging. While conventional AMs require a bulky setup of optical devices for the pumping and optical readout of atomic spin, here, a novel chip-scale single-beam AM scheme is proposed by leveraging extreme transmissive circular polarization dichroism (TCPD) and geometric phase manipulation of spin-selective interference meta-optics. This is achieved through silicon-based metasurfaces that enable the realization of arbitrary-to-circular polarization conversion and wavefront modulation within a monolithic chip at Rb D1 transition wavelength (λ = 795 nm). Two spin-selective interference metasurfaces, i.e., meta-circular-polarizer (MCP) and meta-circular-polarizer-lens (MCPL), are fabricated and characterized, with a measured TCPD of 0.68 for the MCP as well as focusing efficiency and TCPD of around 70.67% and 0.69 for the MCPL, respectively. As a proof of concept, a 4 × 4 × 4 mm³ Rb vapor cell is combined with our metasurface to construct a miniaturized single-beam AM. The sensitivity of our compact metasurface-based system is about 15 fT/Hz^1/2, with a dynamic range near zero-field of ± 2.2 nT. We envision that this work could facilitate the development of burgeoning chip-scale quantum sensors, which hold great potential for high-spatial-resolution biomagnetic imaging, on-chip nuclear magnetic resonance, and so forth.