Metasurface enabled optical regulation for integrated dual-beam optically pumped magnetometers

Abstract

Optically pumped magnetometers (OPMs) have shown great potential for biomagnetic measurements due to high sensitivity and non-invasive operation. On-chip integration has emerged as a key route toward miniaturized optically pumped magnetometers capable of high-spatial-resolution imaging. However, conventional planar microfabricated vapor cells make it difficult to implement on-chip dual-beam configurations, while single-beam schemes are susceptible to laser amplitude noise and therefore struggle to meet ultrahigh-sensitivity requirements. This paper proposes a metasurface enabled on-chip dual-beam optically pumped magnetometer, which is integrated as a vapor-cell window and used to steer the probe beam through phase-gradient modulation, enabling effective spatial overlap between the pump and probe beams inside the atomic vapor cell. Differential detection is introduced to suppress optical source noise and improve the measurement signal-to-noise ratio. A theoretical model of the magneto-optical response under oblique incidence is established, and two-dimensional finite-difference time-domain (FDTD) simulations are conducted to validate the beam-control capability of the metasurface. The optimized phase-shifting unit with a period of 0.4 μm achieves full 2π phase coverage with an amplitude retention above 80%. This planar metasurface-based approach eliminates bulky optical components and provides a compact optical-routing strategy for high-sensitivity on-chip optically pumped magnetometers.