Limits to Resolution of CW STED Microscopy

We report a systematic theoretical and experimental study of the limits to spatial resolution for stimulated emission depletion (STED) superresolution fluorescence microscopy using continuous wave (CW) laser beams. We develop a theoretical framework for CW STED imaging from point fluorescent emitters and calculate the dependence of 2D spatial resolution on the power of the CW excitation (pump) beam, as well as the power, contrast, and polarization of the CW STED “doughnut” beam. We perform CW STED experiments on (non-bleaching) nitrogen vacancy (NV) color centers in diamond and find good agreement with the theoretical expressions for CW STED spatial resolution. Our results will aid the optimization and application of CW STED microscopy in both the physical and life sciences.Physic