Plasmon Localization Assisted by Conformal Symmetry

TL;DR

This paper introduces a transformation optics-based method to design plasmonic metasurfaces that can trap surface plasmon polaritons, enabling ultra-slow light propagation and enhanced light-matter interactions for various nanophotonic applications.

Contribution

It presents a universal design strategy for stopped-light plasmonic metasurfaces leveraging conformal symmetry and transformation optics, applicable across different material systems.

Findings

Achieves ultra-slow group velocities for surface plasmons.

Enables spatial localization of plasmons over their entire lifetime.

Applicable to metallic systems, doped semiconductors, and 2D materials.

Abstract

Plasmonic systems have attracted remarkable interest due to their application to the subwavelength confinement of light and the associated enhancement of light-matter interactions. However, this requires light to dwell at a given spatial location over timescales longer than the coupling rate to any relevant loss mechanism. Here we develop a general strategy for the design of stopped-light plasmonic metasurfaces, by taking advantage of the conformal symmetry which underpins near-field optics. By means of the analytical technique of transformation optics, we propose a class of plasmonic gratings which is able to achieve ultra-slow group velocities, effectively freezing surface plasmon polaritons in space over their whole lifetime. Our method can be universally applied to the localization of polaritons in metallic systems, as well as in highly doped semiconductors and even two-dimensional conductive and polar materials, and may find potential applications in nano-focusing, nano-imaging, spectroscopy and light-harvesting.