Fig. 1: Emitter optical properties and laser-induced charge dynamics.

a Schematic of the system. A single V2 centre in SiC is surrounded by charges (yellow circles) associated to intrinsic residual impurities³⁵. Under laser illumination, these charges can be mobilised after excitation to (from) the conduction (valence) band, indicated by blue and red wiggly lines. b Energy diagram, depicting the V2 centre’s optical transitions (left) and possible laser-induced charge dynamics of the (unknown) impurities in the environment (right). The spin-dependent A₁ and A₂ transitions can be excited with a tunable, near-infrared (NIR) laser (916 nm, red arrow), while a high-energy repump laser (785 nm, blue arrow) is used to scramble the charge state of the V2 centre and its environment. The ground-state spin (\(S=\frac{3}{2}\)) can be manipulated with microwave (MW) radiation. c Scanning-electron-microscopy image of a sample used in this work, which is diced from a 4 inch commercially available 4H-SiC bulk wafer. Nanopillars (~500 nm diameter) are fabricated to improve the photon collection efficiency. d Representative low-temperature (4K) emission spectrum of a V2 centre under repump-laser excitation, showing the characteristic zero-phonon line at 916 nm (red highlight). e Experimental sequence of the diffusion-averaged photoluminescence-excitation spectroscopy (PLE). The frequency f₁ of the NIR laser (red) is scanned over the V2 zero-phonon line, while emission in the phonon sideband is collected. The repump laser (blue) scrambles the charge state of the emitter and its environment before every repetition (total N). f Measured PLE spectrum. Averaging over many charge-environment configurations results in a single, broad peak (2.4(1) GHz FWHM) that encompasses the A₁ and A₂ transitions (separated by ~1 GHz). The laser frequency is offset from 327.10 THz.