Photoinduced Modification of Single-Photon Emitters in Hexagonal Boron Nitride

Fluorescent defects recently observed under ambient conditions in hexagonal boron nitride (h-BN) promise to open novel opportunities for the implementation of on-chip photonic devices that rely on identical photons from single emitters. Here we report on the room-temperature photoluminescence dynamics of individual emitters in multilayer h-BN flakes exposed to blue laser light. Comparison of optical spectra recorded at successive times reveals considerable spectral diffusion, possibly the result of slowly fluctuating, trapped-carrier-induced Stark shifts. Large spectral jumps - reaching up to 100 nm - followed by bleaching are observed in most cases upon prolonged exposure to blue light, an indication of one-directional photochemical changes possibly taking place on the flake surface. Remarkably, only a fraction of the observed emitters also fluoresce on green illumination, suggesting a more complex optical excitation dynamics than previously anticipated and raising questions on the physical nature of the crystal defect at play.