Weak Measurement Enhanced Localization of Nanoparticles Using Structured Light

Abstract: In this work we elaborate on a position sensing technique based on far field polarization measurements. In particular, we apply the weak measurement ansatz to the light scattered by a single nano-antenna. We excite gold nanoparticles resonantly using a polarization tailored focused light beam. The dipole moment of the nanoparticle depends on the position of the particle within the focal field. To determine the dipole moment, we investigate the scattered light in the far field. Moreover, to be able to detect minor changes of the dipole moment we project the polarization onto a Cartesian basis and mix TE- and TM-components of the scattered light in a suited ratio. This postselection is similar to that used in weak measurements. To proof the concept, we investigate different ratios of TE- and TM- components and compare our experimental results with a theoretical model.