Identification of the orientation of a single NV center in a nanodiamond using a three-dimensionally controlled magnetic field

A nanodiamond embedding a single nitrogen-vacancy (NV) center has outstanding optical properties since it is readily manipulated and coupled with nanophotonic devices. Reliable methods to identify the orientation of an NV axis on photonic platforms are important to precisely estimate the coupling efficiency between them. We report on a method to identify the orientation of an NV axis. The proposed method consists of a single dataset of optically detected magnetic resonance (ODMR) measurements taken while rotating the magnetic field in a plane and a single ODMR measurement taken while applying the magnetic field in a single direction. By applying this method to a nanodiamond with a single NV center on a microscope coverslip, the orientation of the NV center is determined to be $(θNV, ϕNV)=(144.6°, 52.9°)$ when the magnetic field is scanned in the xy-plane. When the magnetic field is scanned in the xz-plane, it is determined to be $(θNV, ϕNV)=(148.0°, 45.7°)$ which is consistent within 5.2°. This technique will advance progress toward realizing photon-based quantum networks and quantum communication.