Wide-field AC magnetic field imaging with nitrogen-vacancy centers in diamond

Imaging of AC magnetic fields is crucial for a wide range of diverse applications, from life sciences to microwave (MW) technologies to integrated circuit failure analysis and beyond. Magnetometry based on nitrogen-vacancy (NV) centers in diamond represents a powerful tool, as it allows micron-scale resolution, millimeter-scale field of view, high sensitivity, and non-invasive magnetic field imaging compatible with a large variety of samples. However, it has mostly been used for imaging static or low frequency magnetic fields. In this work, we used an ensemble of NV centers in diamond to achieve wide-field imaging of AC magnetic fields produced by a high frequency (GHz range) MW current running through a test device consisting of a fabricated 100-μm-wide copper wire as well as other microwave antennae. In our microscope, an omega loop is used to drive Rabi oscillations within the NV spin-states and the contribution of the MW field generated by the device-under-test was measured through local variations in the Rabi frequency. Our protocol allowed to obtain AC magnetic field maps with a measured magnetic field sensitivity of ~ 1.6 µT Hz^-1/2, over a field of view of 340x340 µm² with spatial resolution of ~ 1 µm, and a dynamic range of 25 dB.