  Among hundreds of impurities and defects in diamond, the nitrogen-vacancy
(NV) center is one of the most interesting to be used as a platform for quantum
technologies and nanosensing. Traditionally, synthetic diamond is irradiated
with high-energy electrons or nitrogen ions to generate these color-centers.
For precise positioning of the NV centers, fs-laser irradiation has been
proposed as an alternative approach to produce spatially localized NV centers
in diamond. However, most of the studies reported so far used high-repetition
rate fs-laser systems. Here, we studied the influence of the irradiation
conditions on the generation of NV$^-$. Specifically, we varied pulse fluence,
laser focusing, and the number of pulses upon irradiation with 150 fs pulses at
775 nm from a Ti:sapphire laser amplifier operating at 1 kHz repetition rate.
Optically Detected Magnetic Resonance (ODMR) was used to investigate the
produced NV centers, revealing a sizeable zero-field splitting in the spectra
and indicating the conditions in which the lattice strain produced in the
ablation process may be deleterious for quantum information applications.
