Purcell Enhancement and Spin Spectroscopy of Silicon\nVacancy Centers in Silicon Carbide Using an Ultrasmall Mode-Volume\nPlasmonic Cavity

Silicon\nvacancy (V<sub>Si</sub>) centers in 4H-silicon carbide\nhave emerged as a strong candidate for quantum networking applications\ndue to their robust electronic and optical properties, including a\nlong spin coherence lifetime and bright, stable emission. Here, we\nreport the integration of V<sub>Si</sub> centers with a plasmonic\nnanocavity to Purcell enhance the emission, which is critical for\nscalable quantum networking. Employing a simple fabrication process,\nwe demonstrate plasmonic cavities that support a nanoscale mode volume\nand exhibit an increase in the spontaneous emission rate with a measured\nPurcell factor of up to 48. In addition to investigating the optical\nresonance modes, we demonstrate an improvement in the optical stability\nof the spin-preserving resonant optical transitions relative to the\nradiation-limited value. The results highlight the potential of nanophotonic\nstructures for advancing quantum networking technologies and emphasize\nthe importance of optimizing emitter–cavity interactions for\nefficient quantum photonic applications.