Nanoscale Vector Magnetometry with a Fiber‐Coupled Diamond Probe

A nanoscale vector magnetometer is demonstrated by integrating a microfabricated diamond probe with a nanopillar on top of a single‐mode optical fiber. Based on the recently developed self‐aligned patterning techniques, ≈80 nitrogen vacancies are concentrated at a 100 nm 2 area at the center of nanopillars to maximize the excitation and collection efficiencies. The spatial resolution of such a fiber‐coupled diamond magnetometer can reach 100 nm for the first time with a sensitivity of 11.27 µT/ for DC magnetic field sensing. In addition, the probe can provide deterministic oriented diamond nanopillars for simplified vector magnetometry. This fiber‐coupled diamond probe is applied to demonstrate the magnetic field imaging of charged electrodes in a confined box. These results mark a decisive step toward fiber‐based applications with nanoscale vector magnetometry capabilities.