Polarization and coherence of light in nanostructures
Experimental Condensed Matter Physics
Final Report Abstract
The project aimed to study the polarization properties of complex optical fields such as those found in the focal region of high numerical aperture objectives or near optical nanostructures such as plasmonic nanoantennas or optical metasurfaces. The information concerning the polarization properties is contained in the three-dimensional coherence matrix. To map the polarization properties with high spatial resolution, which is necessary for fields confined to the subwavelength scale, a novel type of polarimeter was developed. The polarimeter is based on studying the polarization properties of light scattered by a spherical gold nanoparticle, which acts as a local probe. The spherical shape of the particle is essential as it guarantees the polarization independent response of the particle. In this way the information about the polarization properties is transmitted to the detector undistorted. The main results of the project were the development of a novel concept for nanoscale three-dimensional polarimetry and its theory, implementation of the novel polarimetry method in an experimental setup, and first studies of tightly focused light. The polarimetry method is built around polarimetric Fourier-microscopy. We could show that, surprisingly, a reduced number of polarization measurements are required in comparison to classical polarimetry when the measurements are performed in a Fourier-microscope. This allowed simplifying the experimental approach, which can be important for applications. The first experiments with tightly focused light demonstrated complex patterns of the correlations between field components in the focal region. This research will be continued, one interesting direction of study is for example topological polarization states or the influence of spatial coherence on the polarization states of tightly focused light.
