Optical manipulation of the charge state of nitrogen-vacancy center in diamond

The conversion between two nitrogen vacancy (NV) center charge states (NV0 and NV−) was experimentally studied with laser in the range from 378 to 492 nm. The wavelength and power dependent charge state conversion was proved to be single-photon process at short wavelength and two-photon process at long wavelength. Also, the presence of metastable state in NV− significantly affected the conversion process, which can be used to increase NV− population from 72.5% to 80.5% by applying a magnetic field under 532 nm excitation. The method can be used for improving the fidelity of charge state polarization and subsequently optimizing the quantum control with NV center and resolution in the magnetometric and biological sensoring.