Manipulation of Spin Polarization Using NV Ensemble in Diamond for Precision Displacement Detection With an Adjustable Sensitivity

Magnetic sensing based on nitrogen-vacancy (NV) centers in diamond have been considered by scientists to be a promising candidate for highly sensitive, integrated solid-state quantum sensors. In this paper, a displacement detection system is presented relying on the quantum magnetic effect of NV ensemble under a microwave (MW), which consists of a fluorescence microscope system and a bundle of movable current-carrying coils. The fluorescence microscope system is responsible for efficient fluorescence excitation and collection to identify the energy level splitting of electron spin. Moreover, the current-carrying coils are responsible for creating a gradient magnetic field with high linearity. Measurement by experiment, the theory sensitivity limit of the proposed device can up to 2.713 nm/Hz 1/2 , and the noise sensitivity is 51.93~\mu \text{m} /Hz 1/2 when the coils carry the current 0.1 A. The response of fluorescence intensity (PL) to displacement can be up to 0.493%/mm for \vert + 1\rangle sublevel with a measurement range of 12.57 mm and 0.419%/mm for \vert - 1\rangle sublevel with a measurement range of 13 mm. Through experimental verification, the sensitivity and response can increase proportionally with the current, while the measurement range is inversely reduced. In view of this, the proposed displacement detection system can be used in displacement detection applications of different precision.