Detection of sub-nanotesla magnetic fields by linewidth narrowing in high-density nitrogen vacancy magnetometry with pulsed ESR method

Abstract

Contrast and linewidth, which depend on the microwave (MW) and light powers, are critical for optimizing magnetometer sensitivity based on high-density nitrogen vacancy (NV) centers in diamond. Therefore, the tradeoff between laser and MW powers can be adjusted to optimize the contrast and linewidth extracted from the magnetic resonance. In this paper, we developed a pulsed electron spin resonance (ESR) measurement to enhance the magnetic field sensitivity of an NV magnetic sensor with high-density NV centers in diamond by narrowing the linewidth while keeping the contrast almost constant. Furthermore, for a wide range of experimental settings of MW and light powers in the continuous-wave (CW) method, the contrast and linewidth always increase with increasing MW power. However, by using a simple pulsed ESR sequence based on the repetitive excitation of NV centers, linewidth broadening under relatively high MW power is avoided. The magnetic field sensitivity reaches less than by eliminating the power broadening of the linewidth of ESR, which is one third of that achieved using CW measurements. Finally, the possibility of enhancing magnetic-field sensitivity utilizing the light-narrowing effect is discussed.