Directional Plasmonic Excitation by Helical Nanotips

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, like 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 a nanostructure.

Breaking the Symmetry of a Metal–Insulator–Metal-Based Resonator for Sensing Applications

“…Surface plasmon polaritons (SPPs) are the surface resonant excitations, including electromagnetic (EM) wave and collective electronic motions simultaneously, that the excitation happens at the interface of metal-dielectric boundary [1][2][3][4][5][6][7][8][9]. SPP waves have broad-ranging applications in optical devices and integrated optical circuits (IOCs) due to their advantage of overcoming diffraction limits and confining the light within the subwavelength regime [10][11][12][13][14][15]. As a result, different configurations of optical devices depending on SPP waveguides have been investigated and designed, such as absorbers [16,17], filters [18,19], amplifiers [20,21], switches [22,23], sensors [24][25][26][27][28].…”