LAUSR

Weproposed amethod to effectively fabricate negatively charged nitrogen vacancy (NV) centers close to the diamond surface by applying femtosecond laser writing technique.With a thick layer of silicon (Si) nanoballs coated, diamond surfacewas irradiated by high-fluence femtosecond laser pulses. A large number ofNV centers were created around the laser ablation crater areawithout thermal annealing. The distribution of theNV centers was expanded to about 50μmaway from the crater center. To demonstrate the function of Si nanoballs, we performed the exactly same laser illumination process on the bare region of the sample surface. In this case, only a fewNV centers were generated around ablation crater. At distance of 32μmaway from crater centers, theNV density for the casewith nanoballs was up to 15.5 times higher compared to the casewithout nanoballs. Furthermore, we also investigated the influence of laser fluence and pulse number on the NV density for the casewith Si-nanoball layer. Finally, the formationmechanismofNV centers and the role of Si nanoballs were explained via Coulomb explosionmodel. Themethod is demonstrated to be a promising approach to efficiently and rapidly fabricateNV centers close to the surface of the diamond, which are significant in quantum sensing. Furthermore, the results provide deep insights into complex light-matter interactions.