Two-dimensional optical plasmons with mixed polarization on anisotropic resonant metasurface

TL;DR

This paper presents the first experimental polarization-resolved measurement of 2D optical plasmons on an anisotropic metasurface, revealing mixed polarization states and complex dispersion properties, advancing surface photonics device design.

Contribution

It introduces the first direct experimental measurement of polarization-resolved dispersion of 2D optical plasmons on anisotropic metasurfaces, highlighting mixed TE- and TM-like polarizations and complex isofrequency contours.

Findings

Supported unusual optical surface waves with mixed polarizations.

Identified dipole and quadrupole dispersion bands through simulations.

Observed drastic changes in isofrequency contours with frequency.

Abstract

Optical metasurfaces have great potential to form the platform for manipulation of surface waves. A plethora of advanced surface-wave phenomena utilizing negative refraction, self-collimation and channeling of 2D waves can be realized through on-demand engineering of dispersion properties of a periodic metasurface. In this letter, we report on the first-time direct experimental polarization-resolved measurement of dispersion of 2D optical plasmons supported by an anisotropic metasurface. We demonstrate that a subdiffractive array of strongly coupled resonant anisotropic plasmonic nanoparticles supports unusual optical surface waves with mixed TE- and TM-like polarizations. With the assistance of numerical simulations we identify dipole and quadrupole dispersion bands. The shape of isofrequency contours changes drastically with frequency exhibiting nontrivial transformations of their curvature and topology that is consistently confirmed by the experimental data. By revealing polarization degree of freedom for surface waves, our results open new routes for designing of planar on-chip devices for surface photonics.