Microfabricated Active Laser Noise Suppression Device for a High-Sensitivity Diamond Quantum Magnetometer

Nitrogen vacancy (NV) centers in diamonds have emerged as one of the most promising candidates for magnetic field sensing. However, the laser intensity fluctuation is coupled to the diamond fluorescence; thus, the sensitivity is severely affected by the noise and stability of the laser. Integrating both the diamond quantum sensor and laser noise suppression device is a crucial step toward miniaturization and practical applications. Here, we present a piezoelectric-driven device to dynamically adjust the laser noise cancelation with dimensions of 5 × 5 × 1.5 mm³ based on a grating interferometer. This device incorporates a grating structure to produce diffracted reference light with high-accuracy intensity modulation, actively tracking the fluorescence signal for differential common-mode rejection (CMR), effectively eliminating laser noise in the system, whereby the sensitivity of magnetic field detection is increased by a factor of 34, reaching 160 pT · Hz^–1/2, and beneficial to the long-term stability. The compact design of this laser noise suppressor, in combination with a miniaturized diamond magnetometer, demonstrates its potential for high-precision magnetic field detection ability and strong portability.