Solid-State Optical Magnetometer: Next-Generation Approach to Sub-Nanotesla Magnetic Sensing

We present a Solid-State Optical Magnetometer (SOM) based on black phosphorus (BP) multilayers, offering a compact, scalable, and highly sensitive alternative to traditional atomic-based magnetometers. Utilizing BP's intrinsic linear dichroism in a metasurface cavity, the SOM achieves sub-nanotesla precision and vector magnetic field sensing. BP enhances light-matter interactions, enabling tunable optical responses driven by Lorentz force-induced cavity deformation. Optimized metasurface unit cells increase polarization-dependent absorption, improving detection sensitivity. Finite Element Method simulations show high linearity (R-squared > 0.999), tunable dynamic range, and adjustable sensitivity via current modulation. At 200 microamps, the SOM reaches a sensitivity of 31.25 picotesla, while lower currents expand the dynamic range up to +-10 nanotesla. This tunability allows for application-specific optimization in areas such as biomagnetic sensing, metrology, and industrial field detection. Unlike SQUIDs and optically pumped magnetometers, the BP-based SOM operates at room temperature and nanoscale dimensions with comparable sensitivity, eliminating the need for cryogenics or vapor cells. Power consumption remains under 1 microwatt, far below conventional technologies. This work establishes BP metasurface integration as a promising platform for low-power, miniaturized, and high-performance magnetic field sensing.