The Fiber Self-Focusing Integrated Nitrogen Vacancy Magnetometer.

Quantum magnetic sensing technology utilizing diamond nitrogen vacancy (NV) color centers exhibits high spatial resolution, sensitivity, and dynamic range. The practical applications of the NV color centers magnetometer are limited by its complex system and large volume. To expand the range of applications, it is necessary to improve the integration level of NV color centers magnetometer while meeting the requirements of high portability and sensitivity. In this article, we designed a portable integrated NV magnetometer, and utilized the continuous wave optically detected magnetic resonance (CW-ODMR) method to detect magnetic field. We coupled a micro self-focusing lens with a fiber to create a fiber self-focusing integrated module (FSFI) and bonded a diamond to the other end of the lens. This module was applied to the integrated NV magnetometer. This arrangement ensured uniform intensity of the laser and expanded the irradiation area on the diamond, thereby improving the excitation efficiency of the NV color centers and the number of NV color centers involved in sensing. The magnetometer integrated a microwave antenna module and a fluorescence collection and processing module. The magnetometer was packaged using 3D printing technology and occupied a volume of 10 cm³. After conducting experimental tests, the sensitivity of the magnetometer was 9.6 nT/Hz ^1/2 , and the photon shot noise limited sensitivity can reach 0.85 nT/Hz ^1/2 . The maximum detection relative error of the DC magnetic field was 0.848%, and the detection bandwidth was 40 Hz. The signal-to-noise ratio (SNR) of the AC magnetic field was 28.107 dB within the detectable bandwidth. The integrated NV magnetometer exhibits excellent performance in detecting magnetic fields and offers strong portability. In various fields including magnetic anomaly localization, battery current detection, and medical diagnosis, it possesses significant potential for application.