RESUMO
We report on the experimental demonstration of improved lateral resolution in stimulated emission depletion (STED) microscopy using an annular depletion beam configuration. A tight and finely tuned doughnut focal spot can be created by annular vortex illumination. Its application in STED microscopy for enhanced lateral resolution is systematically investigated by imaging 40 nm fluorescent beads. An improved resolution with more than 20% reduced effective point spread function of the imaging system determined by the full width at half-maximum compared to that of the conventional STED is achieved. The proposed scheme also demonstrates its resolving capability for biological samples. The principle holds great potential in the research fields of biological superresolution imaging as well as STED-based nanolithography and high-density optical data storage.