Enhanced sensitivity of the nitrogen-vacancy ensemble magnetometer via surface coating

Abstract

Magnetometers based on nitrogen-vacancy center ensembles in diamond have received considerable attention in recent years. However, their sensitivities are limited by low fluorescence collection efficiencies. With the introduction of some schemes, collection efficiencies of NV ensembles have been improved, but further improvement is still needed. In this Letter, we propose and demonstrate a fluorescence enhancing technique of reflective coating. By applying this technique, collection efficiencies already improved by other schemes will be further enhanced. With the assistance of a 100-nm-thick gold reflective film on the diamond surface, the fluorescence collection efficiency of an NV ensemble continuous-wave magnetometer utilizing a compound parabolic concentrator was further increased by 92%, and a magnetic field sensitivity of 164 pT/Hz at 0.99 to 77.98 Hz was achieved.