Near-Field Analysis of Bright and Dark Modes on Plasmonic Metasurfaces Showing Extraordinary Suppressed Transmission

TL;DR

This paper investigates plasmonic metasurfaces with subwavelength silver patterns, revealing how bright and dark modes are excited and propagate, leading to extraordinary suppression of transmission in the visible range.

Contribution

It provides a near-field analysis distinguishing bright and dark plasmonic modes on ultrathin metasurfaces, enhancing understanding of their excitation and propagation behaviors.

Findings

Bright modes are resonantly excited on metal ridges.

Dark surface plasmon polaritons propagate across the metasurface.

The metasurface achieves extraordinary suppression of transmission.

Abstract

Plasmonic metasurfaces are investigated that consist of a sub wavelength line pattern in an ultrathin (~ 10 nm) silver film, designed for extraordinarily suppressed transmission (EOST) in the visible spectral range. Measurements with a near-field scanning optical microscope (NSOM) demonstrate that far field irradiation creates resonant excitations of antenna like (bright) modes that are localized on the metal ridges. In contrast, bound (dark) surface plasmon polaritons (SPPs) launched from an NSOM tip propagate well across the metasurface, preferentially perpendicular to the grating lines.