Engineering Novel optical sensors for magnetic field sensing applications

Magnetic field detectors have wide applications, particularly in low-field medical imaging such as MRI. Classical detection methods, including inductive coils and superconducting quantum interference devices (SQUIDs), as well as atomic vapor magnetometers (AVMs), are well established but limited by cryogenic requirements and size constraints that hinder integration into compact medical devices. Nitrogen-vacancy (NV) centers in diamond offer a promising alternative, combining long spin coherence times at room temperature, efficient optical readout, and high spatial resolution.This dissertation provides an exploratory study addressing material science, microwave engineering, and magnetometry challenges in NV-based sensing. First, we investigated the potential of polycrystalline diamonds (PCDs) grown over non-diamond substrates to host large NV⁻ ensembles, identifying an optimal nitrogen flow rate of 10 sccm for NV⁻ formation. We further characterized how nitrogen flow rate affects surface morphology, grain orientation, and NV charge state, proposing a mechanism to explain NV⁰ dominance in low-pressure growth regimes.Second, we designed and constructed a novel NV sensor using a non-confocal illumination scheme. The system achieved a magnetic field sensitivity of approximately 0.2 μT/√Hz in a Halbach magnet configuration using optically detected magnetic resonance (ODMR). These results establish a foundation for scalable, cost-effective NV sensors for wide-field magnetic sensing applications.