Tomographic STED microscopy.

Stimulated emission depletion (STED) microscopy is a versatile imaging method with diffraction-unlimited resolution. Here, we present a novel STED microscopy variant that achieves either increased resolution at equal laser power or identical super-resolution conditions at significantly lower laser power when compared to the classical implementation. By applying a one-dimensional depletion pattern instead of the well-known doughnut-shaped STED focus, a more efficient depletion is achieved, thereby necessitating less STED laser power to achieve identical resolution. A two-dimensional resolution increase is obtained by recording a sequence of images with different high-resolution directions. This corresponds to a collection of tomographic projections within diffraction-limited spots, an approach that so far has not been explored in super-resolution microscopy. Via appropriate reconstruction algorithms, our method also provides an opportunity to speed up the acquisition process. Both aspects, the necessity of less STED laser power and the feasibility to decrease the recording time, have the potential to reduce photo-bleaching as well as sample damage drastically.