Directional Plasmonic Excitation by Helical Nanotips.

Leeju Singh,Nicolò Maccaferri,Denis Garoli,Yuri Gorodetski

doi:10.3390/nano11051333

Abstract

The phenomenon of coupling between light and surface plasmon polaritons requires specific momentum matching conditions. In the case of a single scattering object on a metallic surface, such as a nanoparticle or a nanohole, the coupling between a broadband effect, i.e., scattering, and a discrete one, such as surface plasmon excitation, leads to Fano-like resonance lineshapes. The necessary phase matching requirements can be used to engineer the light–plasmon coupling and to achieve a directional plasmonic excitation. Here, we investigate this effect by using a chiral nanotip to excite surface plasmons with a strong spin-dependent azimuthal variation. This effect can be described by a Fano-like interference with a complex coupling factor that can be modified thanks to a symmetry breaking of the nanostructure.

Highlights

IntroductionNanomaterials 2021, 11, Fano interference is a well-known physical phenomenon that occurs when two oscillating systems interact, one of which is characterized by a narrow resonance and the other having a broadband response [1,2,3]
In Equation (2), this broadband scattering is represented by common temporal ellipticity variation), the results presented unity while the coupling of the scattered light to the plasmonic wave is represented by the here show k-space maps of the ellipticity
We experimentally observed a strong directionality of plasmonic waves excited by a chiral nanotaper resulted from a spatial Fano-like effect

Summary

Introduction

Nanomaterials 2021, 11, Fano interference is a well-known physical phenomenon that occurs when two oscillating systems interact, one of which is characterized by a narrow resonance and the other having a broadband response [1,2,3]. In such a case, an asymmetric lineshape of the resonance with respect to the driving force frequency [4] should appear. The Fano lineshape tuning in nanostructures by complex phase matching conditions was recently demonstrated by using circularly polarized light impinging on a subwavelength scatterer to excite a radially propagating plasmonic wave [11,12]. It has been shown that this directionality was strongly dependent on the handedness of the circular polarization state—the incident spin

Methods

Results

Conclusion