Integrated waveguides and deterministically positioned nitrogen vacancy centers in diamond created by femtosecond laser writing
Robust coupling of nitrogen vacancy centers to integrated optical devices will be crucial for future scaling of on-chip quantum optical systems. In this work, the authors demonstrate the fabrication of type II optical waveguides and the creation of accurately placed NV- (nitrogen vacancy in negative charge state) defect centers using the same femtosecond laser inscription setup. Critically, the pre-fabricated waveguides survive the high-temperature annealing stage required to create stable NV- centers. Optical characterization of the laser-written NV- center confirms single photon emission and coupling to the waveguide mode. This flexible fabrication method not only exhibits high positional accuracy, but it also allows the creation of devices within the bulk of the material, avoiding surface effects that can be detrimental to shallow defects in diamond. Development of optical building block components such as evanescent field couplers and waveguide bends will open up many applications for this technology and the potential for future 3D optical devices in diamond.