Polarization tomography of metallic nanohole arrays

We report polarization tomography experiments on metallic nanohole arrays with square and hexagonal symmetry. As a main result, we find that a fully polarized input beam is partly depolarized after transmission through a nanohole array. This loss of polarization coherence is found to be anisotropic, i.e. it depends on the polarization state of the input beam. The depolarization is ascribed to a combination of two factors: i) the nonlocal response of the array due to surface plasmon propagation, ii) the non-plane wave nature of a practical input beam.