Optical control of color centers in hexagonal boron nitride

We present two multi-color optical excitation techniques to probe quantum emitters in the two-dimensional semiconductor, hexagonal boron nitride. Firstly, we demonstrate controllable optical switching with different color lasers between optically bright and dark states of the color centers. Secondly, we use stimulated emission depletion (STED) as a spectroscopic probe, complementary to photoluminescence excitation spectroscopy, and reveal differences between the electron-phonon interaction in the ground and excited states. Finally, we show that hBN color centers are a viable fluorophore for STED imaging, achieving a spatial resolution of ∼ 50 nm.