Polarization conversion of non-specular diffraction orders from metallic nanohole arrays studied by Fourier space polarimetry

TL;DR

This study investigates how diffraction orders from a metallic nanohole array exhibit polarization rotation and ellipticity changes, especially when surface plasmon polaritons are excited, using Fourier space polarimetry and simulations.

Contribution

It provides new insights into polarization conversion phenomena in nanohole arrays, highlighting the role of surface plasmon polaritons and angular dependence, supported by experimental and simulation data.

Findings

No polarization conversion in diffraction orders in the incident plane.

Significant polarization changes occur in diffraction orders out of the incident plane.

Surface plasmon polaritons cause dramatic shifts in rotation angle and ellipticity.

Abstract

We use Fourier space polarimetry to study the incident angle- and polarization-dependent rotation angle and ellipticity of different diffraction orders emerging from a two-dimensional periodic Au array. The array has square lattice and circular nanoholes and thus is achiral. We find no polarization conversion occurs if the diffraction orders lie in the incident plane. However, for the orders that are diffracted away from the incident plane, their rotation angle and ellipticity vary considerably with incident angle and polarization. In particular, dramatic changes in rotation angle and ellipticity are observed when Bloch-like surface plasmon polaritons (SPPs) are excited. The experimental results are consistent with the finite-difference time-domain simulations. The transverse spin carried by the SPPs and a discrete dipole model are used complementarily to elucidate such angular and polarization dependences.