Fiber-integrated N-V diamond magnetometer compatible with commercial endoscopic systems

Abstract

The nitrogen-vacancy (N-V) center in diamond provides a robust, solid-state platform for magnetic field measurements at room temperature. To harness its potential in inspecting inaccessible regions, here we present a compact endoscopic configuration of a N-V diamond–based magnetometer. The endoscopic magnetometer was developed by integration of a large-core optical fiber with a bulk N-V diamond for laser excitation and photoluminescence (PL) collection. The diamond and fiber were specially shaped to enhance PL collection through the fiber. Additionally, a three-dimensionally-printed endoscope head was used to facilitate alignment of the bias magnetic field along the N-V axis. A magnetic field sensitivity of approximately 3 nT/√Hz at 20 Hz was achieved by continuous-wave magnetometry measurements. The endoscope diameter was restricted to 10 mm to match the dimensions of most commercial endoscopes. The magnetic field nonuniformity caused by the small separation between the diamond and the magnet in the endoscope head limited the overall sensitivity. It could be further improved to 0.85 nT/√Hz at 20 Hz by use of a magnet placed at a sufficient distance outside the endoscope head. Our endoscopic design is mechanically stable and provides additional opportunities for integrating other functionalities into the probe head as needed.

The nitrogen-vacancy (N-V) center in diamond provides a robust, solid-state platform for magnetic field measurements at room temperature. To harness its potential in inspecting inaccessible regions, here we present a compact endoscopic configuration of a N-V diamond-based magnetometer. The endoscopic magnetometer was developed by integration of a large-core optical fiber with a bulk N-V diamond for laser excitation and photoluminescence (PL) collection. The diamond and fiber were specially shaped to enhance PL collection through the fiber. Additionally, a three-dimensionally-printed endoscope head was used to facilitate alignment of the bias magnetic field along the N-V axis. A magnetic field sensitivity of approximately 3 nT/root Hz at 20 Hz was achieved by continuous-wave magnetometry measurements. The endoscope diameter was restricted to 10 mm to match the dimensions of most commercial endoscopes. The magnetic field nonuniformity caused by the small separation between the diamond and the magnet in the endoscope head limited the overall sensitivity. It could be further improved to 0.85 nT/root Hz at 20 Hz by use of a magnet placed at a sufficient distance outside the endoscope head. Our endoscopic design is mechanically stable and provides additional opportunities for integrating other functionalities into the probe head as needed.