A Magneto‐Optically Co‐Enhanced Direct‐Readout Diamond NV Fiber‐Optic Vector Quantum Magnetometer

Nitrogen‐vacancy (NV) centers in diamond exhibit magnetic‐field‐sensitive quantum properties and possess four distinct crystallographic orientations, establishing a robust foundation for vector magnetic sensing. However, NV‐based vector magnetic field sensors are plagued by high demodulation complexity and cost arising from cross‐talk among NV orientations, in addition to the challenge of limited sensitivity. Here, we present a diamond NV fiber‐optic planar vector magnetometer that enables direct readout of magnetic components with high sensitivity. This is achieved through a novel alignment scheme based on the NV centers intrinsic orientations, which suppresses cross‐talk to below 2%. Meanwhile, a magneto‐optically co‐enhanced strategy is implemented by integrating two pairs of magnetic flux concentrators and optimizing the polarization of excitation light, leading to a nearly 20‐fold improvement in sensitivity. Furthermore, the real‐time readout capability and overall performance are experimentally validated under dynamic magnetic field variations in realistic scenarios. Our work provides a viable solution for high‐performance NV‐based vector magnetometry with simplified demodulation, facilitating its application in areas such as magnetic anomaly detection.