Wide-field AC magnetic field imaging using continuous-wave optically detected magnetic resonance of nitrogen-vacancy centers in diamond

Nitrogen-vacancy (NV) center in diamond is a promising candidate for a highly-sensitive magnetometer with high spatial resolution at room temperature. Conventional magnetometry typically uses scanning confocal microscopic techniques that require long measurement times to achieve a wide observation area and/or high sensitivity. Wide-field imaging techniques using CCD/CMOS camera has the advantage of enabling a wide field of view and rapid acquisition time by simultaneously detecting signals from NV centers in a large number of pixels of the camera. Continuous-wave optically detected magnetic resonance (CW-ODMR) is suitable for wide-field imaging of magnetic field using cameras with slow response time. However, only DC or low-frequency (up to kHz) AC magnetic field can be detected using CW-ODMR techniques. Recently, our group has developed a new measurement protocol using CW-ODMR to detect high-frequency (MHz range) AC magnetic fields using the zero-field splitting of the spin triplet states of NV centers. This technique is compatible with CCD-based imaging techniques. In this study, we implement our CW-ODMR protocol and measure the spatial-distribution of high-frequency AC magnetic fields with a wide-field imaging setup. Using our home-built wide-field imaging setup, a bulk diamond sample was mounted on a microwave antenna and a target AC magnetic field was applied by a copper wire placed on the sample surface. By comparing the CW-ODMR spectra with and without applied field, it is demonstrated that the AC magnetic field can be detected and estimated according to the protocol. Detection was performed both in wide-field view and windows of few pixels while averaging the signal over many pixels enabled rapid measurements.