An Integrated Widefield Probe for Practical Diamond Nitrogen-Vacancy Microscopy

The widefield diamond nitrogen-vacancy (NV) microscope is a powerful instrument for imaging magnetic fields. However, a key limitation impeding its wider adoption is its complex operation, in part due to the difficulty of precisely interfacing the sensor and sample to achieve optimum spatial resolution. Here we demonstrate a solution to this interfacing problem that is both practical and reliably minimizes NV-sample standoff. We built a compact widefield NV microscope which incorporates an integrated widefield diamond probe with full position and angular control, and developed a systematic alignment procedure based on optical interference fringes. Using this platform, we imaged an ultrathin (1 nm) magnetic film test sample, and conducted a detailed study of the spatial resolution. We reproducibly achieved an estimated NV-sample standoff (and hence spatial resolution) of at most $\sim2~\mu$m across a $\sim0.5$ mm field of view. Guided by these results, we suggest future improvements for approaching the optical diffraction limit. This work is a step towards realizing a widefield NV microscope suitable for routine high-throughput mapping of magnetic fields.