Multi-focal laser fabrication of nitrogen vacancy centres in a bulk diamond

We demonstrate the multi-focal fabrication of single NV− centres at different depths in a bulk diamond. After performing an annealing process, the optically detected magnetic resonance (ODMR) signal is measured to confirm the generation of NV− centres. These emitters are photo-stable and are imaged by using three different excitations wavelengths at different depths close to the bulk diamond surface. Using two-photon microscopy, the NV− centres are imaged with a resolution down to 0.36 µm to study the effect of the exposure time of the multi-focal laser writing on the spatial resolution of each fabrication. The Hanbury Brown and Twiss (HBT) test is performed with two-photon excitation to study the number of NV− centres at the location of each multi-focal fabrication. We demonstrate the formation of single NV− centres placed between 100 nm and 3 µm below the diamond surface. The ability to control the placement of single NV− centres with depth is of paramount importance for applications in quantum information, single spin magnetometry, and optical data storage.