Stimulated Emission Depletion Microscopy with Diamond Silicon Vacancy Centers

The spatial resolution and fluorescence signal amplitude in stimulated emission depletion (STED) microscopy is limited by the photostability of available fluorophores. Here, we show that negatively charged silicon vacancy (SiV) centers in diamond are promising fluorophores for STED microscopy, owing to their photostable, near-infrared emission and favorable photo physical properties. A home-built pulsed STED microscope was used to image shallow implanted SiV centers in bulk diamond at room temperature. The SiV stimulated emission cross section for 765-800 nm light is found to be (4.0 +/- 0.3) X 10(-17) cm(2), which is approximately 2-4 times larger than that of the negatively charged diamond nitrogen vacancy center and approaches that of commonly used organic dye molecules. We performed STED microscopy on isolated SiV centers and observed a lateral fullwidth-at-half-maximum spot size of 89 +/- 2 nm, limited by the low available STED laser pulse energy (0.4 nJ). For a pulse energy of 5 nJ, the resolution is expected to be similar to 20 nm. We show that the present microscope can resolve SiV centers separated by less than or similar to 150 nm that cannot be resolved by confocal microscopy.