Nitrogen-vacancy (NV) centers in diamond have become a key platform for precision sensing of magnetic fields at ambient conditions, offering tunable control and readout of spin states [1-2]. In this work, we compare the coherence properties of NV centers in both bulk diamond and microdiamond samples, examining their performance in DC and AC magnetic field sensing under various pulse sequences—including Ramsey interferometry and dynamic decoupling. By systematically evaluating optically detected magnetic resonance (ODMR), Rabi oscillations, and T₁ and T₂ relaxation times, we identify how different sample forms and control protocols impact sensing sensitivity and coherence.
Our scanning confocal microscopy measurement platform integrates single-photon counting with microwave pulse shaping, pico-second laser excitation and charge dynamics analysis module, thereby enabling optimization of time-resolved control and readout of NV spin states. We demonstrate optimized bulk and single defect ODMR signals, Rabi oscillations, as well as T₁ and T₂ decay profiles. We further show how tailored pulse sequences, such as dynamical decoupling, can enhance sensitivity to both DC and AC magnetic fields across several experimental scenarios.
These results highlight the adaptability and effectiveness of NV-based sensors, with potential applications ranging from fundamental quantum research to nanoscale magnetic imaging. Future work will focus on developing a compact room-temperature operated quantum sensing and information processing platform.