Axial Superlocalization with Vortex Beams

Improving axial resolution is paramount importance for three-dimensional optical imaging systems. Here, we investigate the ultimate precision in axial localization using vortex beams. For Laguerre–Gauss (LG) beams, this limit can be achieved with just an intensity scan. The same is not true for superpositions of LG beams, in particular for those with intensity profiles that rotate on defocusing. Microscopy methods based on rotating vortex beams may thus benefit from replacing traditional intensity sensors with advanced mode-sorting techniques.