Controlled Polarized Optical Excitation Method on Ensembles of Nitrogen-Vacancy Centers in Diamonds

Crystal axes must be distinguished in vector magnetic measurements of ensemble nitrogen-vacancy (NV) centers in diamonds. However, achieving crystal axes distinction in confocal systems without a magnetic bias field is challenging. Thus, a controlled polarized optical excitation method to overcome this problem is proposed. The polarization angle of the excitation beam can be adjusted in free space using an optical pen for higher controllable degrees of freedom. Compared to previous optical excitation methods, the proposed method improves the maximum suppression by 19.2% and the maximum excitation by 42.4%. Moreover, the proposed method has a decoupling effect on NV axis resonances with a similar change trend. This method can easily replace existing optical excitation methods in NV measurement systems and is a powerful tool for ensembles of NV centers' vector measurements without relying on magnetic bias fields. Polarized beams that are intentionally not parallel to the diamond surface are generated, creating a controlled tilt angle. The polarization angle of the excitation beam can be adjusted in free space to improve optical selection. The proposed excitation method can be used for all types of diamonds, and can seamlessly replace existing optical excitation methods in all nitrogen-vacancy (NV) measurement systems.image