Wide-field magnetic field imaging with nitrogen vacancy centers in nanodiamonds at high frame-rates

Abstract

The nitrogen vacancy center (NV) is a promising single spin system in diamond with optical polarization, readout and optically detected magnetic resonances (ODMR). The NV has been shown to be a sensitive magnetometer at room temperature. In particular, owing to their small size, NV centers in nanocrystals (nanodiamonds) offer magnetic field imaging with high spatial resolution. Competitive magnetic field imaging methods such as magnetic force microscopy (MFM) or superconducting quantum interference devices (SQUID) either image serially, and are thus slow, or are limited in their use for biological systems. Nanodiamonds in contrast have the advantage that they can be attached to biological tissues in vivo and can be imaged in parallel at high speeds. Unfortunately, nanodiamonds tend to aggregate due to Coulomb interactions of their surface species. This aggregation results in a inhomogeneous broadening of the NV's ODMR with applied magnetic field. This broadening makes imaging magnetic fields non-trivial. In this work, we present a model to understand aggregated nanodiamonds. Despite NVs with defined crystallographic orientations demonstrating vectorial resolution of magnetic fields, this model predicts that aggregated nanodiamonds should be treated as absolute magnetometers. Further, a sparse sampling protocol is implemented that enables time resolved magnetometry and is used to image the magnetic field of a current carrying wire at greater than 33 Hz speeds with magnetic field sensitivities better than ... over a 10 [mu]m x 10 [mu]m field of view.