Magnetic Field Imaging with an Optical Microscope Using a Quantum Diamond Sensor Add‐On

Abstract Widefield magnetic imaging using ensembles of nitrogen‐vacancy (NV) centres in diamond has emerged as a useful technique for studying the microscopic magnetic properties of materials. Thus far, this technique is mainly implemented on custom‐made optical microscopes. An add‐on is developed for a standard laboratory optical microscope that integrates the NV‐diamond sensor and necessary light source, microwave antenna, and bias magnet, enabling NV‐based magnetic imaging while retaining the typical optical measurement modes of the microscope. The retrofitted quantum diamond microscope is demonstrated by imaging a magnetic particle sample using brightfield, darkfield, and magnetic imaging modes. Furthermore, an iso‐magnetic field imaging technique is employed to visualize the magnetic field of the sample within seconds, and finally demonstrate 3D stray field imaging. Retrofitting existing microscopes exploits the stability and high quality of traditional optical microscope systems while reducing the cost and space requirements of establishing a standalone magnetic imaging system.