Systematic Wavelength-Scale Errors in the Localization of Nanoscale Emitters due to Spin-Orbit Coupling of Light

The precise determination of the position of sub-wavelength scale emitters using far-field optical imaging techniques is of utmost importance for a wide range of applications in medicine, biology, astronomy, and physics. Modern super-resolution techniques allow one to determine the positions of individual emitters in principle with arbitrary precision. In recent years, different technical effects have been discussed that, in such applications, can give rise to an apparent shift of the emitter's position of a few ten nanometres. In my talk, I will demonstrate a novel and fundamental physical effect that leads to systematic, wavelength-scale position errors when imaging elliptically polarized emitters. The effect stems from the orbital angular momentum carried by the light field due to spin-orbit coupling. By imaging a single trapped atom as well as a single gold nanoparticle, we demonstrate that this effect leads to shifts between the emitters' measured and actual positions which are comparable to the optical wavelength.