Compact and Stable Diamond Quantum Sensors for Wide Applications

This study proposes compact, highly sensitive, and stable diamond quantum sensors for a wide range of applications, including biomedical and energy electronics. For enhanced sensitivity and alignment precision within the objective field, a high-quality, (111)-oriented ¹²C-enriched chemical vapor deposition (CVD) diamond, featuring a nitrogen-vacancy (NV) axis in the (111) direction, is employed as the sensor. To increase the fluorescence collection efficiency, the laser beam is irradiated from the side surface of the CVD diamond, and fluorescence is detected using a compound parabolic concentrator (CPC) lens. The floor noise level of the magnetic field signal is 44 pT/Hz^0.5. An Allan deviation of 1.2 pT over 1000 s of averaging demonstrates stability. This is attributable to the integration of a balancing circuit to cancel out laser noise, alongside mechanisms to compensate for temperature fluctuations and a copper housing to shield against electromagnetic field noise.