Abstract
The silicon vacancy (VSi) in 4H-SiC represents a promising candidate for solid-state qubits. However, conventional high-temperature annealing typically suffers from undesired impurity diffusion and limited spatial localization during fabrication. Here, we present a femtosecond laser annealing approach for the in situ restoration and property tunability of VSi color centers in proton-implanted 4H-SiC. By delivering extremely high transient peak temperatures within micrometer-scale thermal interaction zones, lattice damage is effectively eliminated and excessive defect diffusion is suppressed. Specifically, the room-temperature photoluminescence intensity was enhanced to 1.5 times its initial value. The zero-phonon line in low-temperature spectra was markedly sharpened with increased intensity, and efficient relaxation of residual stress in the implanted area was verified via Raman spectroscopy. Regarding quantum properties, the optically detected magnetic resonance contrast was increased by a factor of 1.6. Furthermore, the linewidth was significantly narrowed, and both the transverse/longitudinal coherence times and Rabi oscillation contrast were substantially improved. This work demonstrates that femtosecond laser annealing provides a high-spatial-resolution, nonequilibrium processing strategy, offering substantial utility for the fabrication of high-quality VSi quantum light sources with extended coherence times.