An Integrated Nitrogen-Vacancy Magnetometer With Subnanotesla Sensitivity for Practical Applications

The practical applications require the nitrogen-vacancy (NV) magnetometer to be transportable and highly sensitive. In this study, we have demonstrated a portable NV magnetometer consisting of a sensor head and miniaturized control system with a volume of $22\times 19\times 12$ cm, which can operate outside the laboratory when connected to a computer. The sensor exhibited a sensitivity of 892.7 pT/Hz $^{\text {1/2}}$ , achieved through the use of a fluorescence omni-directional reflection concentrator (FORC) and common mode laser noise rejection (CMR) technology. Notably, the FORC increased the fluorescence collection efficiency to 57% by allowing the collection of fluorescence emitted from all six facets of the diamond. Our work is expected to facilitate the transition of NV magnetometers from a laboratory platform to practical applications.