Near- and Far-Field Excitation of Topological Plasmonic Metasurfaces

TL;DR

This paper investigates topological plasmonic metasurfaces with a breathing honeycomb lattice, demonstrating source-position-dependent directional energy propagation in near- and far-field regimes, with potential applications in nanoscale light guiding.

Contribution

It provides a semi-analytical model for probing topological edge states in plasmonic metasurfaces and establishes conditions for directional excitation dependent on source position.

Findings

Directionality depends on source position.

Circularly polarized magnetic dipoles enhance edge mode emission.

Far-field excitation with orbital angular momentum beams achieves directional control.

Abstract

The breathing honeycomb lattice hosts a topologically non-trivial bulk phase due to the crystalline-symmetry of the system. Pseudospin-dependent edge states which emerge at the interface between trivial and non-trivial regions can be used for directional propagation of energy. Using the plasmonic metasurface as an example system, we probe these states in the near and far-field using a semi-analytical model. We give the conditions under which directionality is observed and show that it is source position dependent. By probing with circularly-polarized magnetic dipoles out of the plane, we first characterize modes along the interface in terms of the enhancement of source emission due to the metasurface. We then excite from the far-field with non-zero orbital angular momentum beams. The position dependent directionality holds true for all classical wave systems with a breathing honeycomb lattice. Our results show that a metasurface in combination with a chiral two-dimensional material could be used to guide light effectively on the nanoscale.