High sensitivity of diamond nitrogen-vacancy magnetometer with magnetic flux concentrators via enhanced fluorescence collection

Diamond nitrogen-vacancy (NV) centers magnetometer is attracting more and more attention due to their room-temperature solid-state property. High sensitivity is crucial for practical applications of diamond NV magnetometers. However, the sensitivity of the diamond magnetometer needs to be improved for weak magnetic measurement. Recent studies have shown that diamond with magnetic flux concentrators (MFC) makes it feasible to achieve low-frequency sensitivity at fT/Hz level. Here, we demonstrate an enhanced fluorescence collection method to improve the sensitivity of diamond NV magnetometer with MFC. A high magnetic field sensitivity of 0.47 pT/Hz (>100Hz) is achieved under resonance conditions, which is about two times higher than that without improved fluorescence collection. We then integrate the diamond magnetometer (probe size ∼8×9×13 cm3) with a shielded sensitivity of 1 pT/Hz (>30Hz). Our method offers a solution for the high-sensitivity diamond NV magnetometer. Thus, this work enables an ultra-compact and scalable platform for quantum sensing based on the diamond NV center technique. Future, diamond NV magnetometers could be proposed used in shipwreck detection, cardiac magnetic field measurement, explosives detection, etc.