Compact and Portable NV Center Magnetometer for Field Application

Abstract

Quantum magnetometry provides high sensitivity, but many prominent quantum magnetometers employ strict cryogenic cooling requirements. NV centers in diamond bypass this fundamental limit, allowing robust magnetic sensing with high sensitivity at room temperature. The main focus of this research is to translate the fundamental physics of NV centers on a tabletop setup to a compact magnetometer optimized for real world application. Initially, the spin dynamics of the NV center based ensemble system were characterized using a PCB microstrip antenna for microwave excitation in a tabletop setup with Optically Detected Magnetic Resonance (ODMR). By employing both continuous wave (CW) and pulsed wave (PW) ODMR protocols, the physical phenomena of both optical and microwave power broadening were isolated using this setup. This setup provided a baseline for the experiment by achieving a shot noise limit magnetic sensitivity of approximately 10nT/[(Hz)^1/2]using this setup. Moreover, the Zeeman splitting of the ms = ±1 spin states under a magnetic field was also characterized and a linear response was observed. Moreover, the observation of distinct resonance peaks for di erent NV orientations also verified the transition from scalar DC amplitude magnetometry to full 3D vector magnetometry. Following the above development, the experimental architecture has been successfully miniaturized into a working fiber optic sensor. By employing the micro-coil antenna and the miniaturized backscatter optical collection system, the sensor has successfully resolved the characteristic ODMR spectrum. Moreover, the magnetometry functionality has been successfully verified by isolating a single NV crystallographic axis using DC magnetic field sweeps. By employing the optimization protocol, the sensor has been able to achieve a working shot noise limited DC magnetic sensitivity of 1.26 µT/[(Hz)^1/2]. In order to overcome the inherent trade offs of the sensor miniaturization process, this thesis has assessed the theoretical intrinsic limits while establishing a physical roadmap toward improved sensitivity through the application of pulsed dynamical decoupling sequences. The overall goal of this research is to provide the framework for the optimization of NV magnetometry, both in a tabletop level and in a portable setup, as well as the analysis and characterization.