Photo-induced charge state dynamics of the neutral and negatively charged silicon vacancy centers in room-temperature diamond

The silicon vacancy (SiV) center in diamond is drawing much attention due to its optical and spin properties, attractive for quantum information processing and sensing. However, the dynamics governing SiV charge state interconversion has been less explored mainly due to challenges associated with generating, stabilizing, and characterizing all possible charge states, particularly at room temperature. In this work we use multi-color confocal microscopy and density functional theory to examine photo-induced SiV recombination from neutral (SiV0), to single (SiV-), to double-negatively charged (SiV2-) over a broad spectral window in chemical-vapor-deposition diamond under ambient conditions. For the SiV0 to SiV‒ transition, we found a linear growth of the photo-recombination rate with laserpower at all observed wavelengths, a hallmark of single photon dynamics. Laser excitation of SiV‒, on the other hand, yields only fractional recombination into SiV2‒, a finding we interpret in terms of a photo-activated electron tunneling process from proximal nitrogen atoms.