Not yet reviewed by Pith; the record is open.

Emerging quantum technologies based on the nitrogen-vacancy (NV) centre in diamond require carefully engineered material with controlled defect density, optimised NV formation processes, and minimal crystal strain. The choice of NV generation technique plays a crucial role in determining the quality and performance of these centres. In this work, we investigate NV centre formation in nitrogen-doped diamond using femtosecond (fs) laser processing. We systematically examine the effect of laser pulse energy on NV production and quality using photoluminescence and optically detected magnetic resonance measurements. We also probe the role of pre-existing lattice defects formed by electron irradiation and consider defect evolution over extended dwell times. Finally, we are able to identify a regime where the main action of the fs-laser is to diffuse rather than create vacancies. This local annealing capability expands the toolkit for tailored NV production and presents opportunities for fine tuning defect populations.