Optimization of depletion focal spot in STED nanoscopy using amplitude manipulation

To optimize the performance of stimulated emission depletion (STED) nanoscopy, a high-quality ring-shaped depletion pattern with a “zero”-intensity point at the center is mandatory. Here, we propose a novel strategy to enhance the two-dimensional (2D) resolution of STED nanoscopy by amplitude manipulation. In particular, we employ an annular mask to the depletion beam to enable a compression to the size of effective point spread function (PSF) by at least 20%.