Deterministic Laser-Writing of Spin Defects in Nanophotonic Cavities

Robust engineering and characterization of spin-defect coupling to nanophotonic cavities remains a challenge in developing scalable quantum network nodes. Here we demonstrate direct laser writing of cavity-integrated spin defects using a nanosecond-pulsed above-bandgap laser. Photonic crystal cavities in 4H-silicon carbide serve as a nanoscope monitoring silicon monovacancy (V_Si^-) defect formation within the 100 nm³ cavity mode volume. We observe spin resonance, cavity-integrated photoluminescence, and excited-state lifetimes consistent with conventional defect formation methods, without need for post-irradiation thermal annealing. We further find an exponential reduction in excited state lifetime at fluences approaching the cavity amorphization threshold, and show single-shot laser annealing of intrinsic background defects at V_Si^- formation sites.