Electron Energy Loss Spectroscopy of Singular Plasmonic Metasurfaces

Abstract

Singular plasmonic metasurfaces, which feature sharp edges or ultra‐small gaps, are characterized by a continuous excitation spectrum that results in broadband light‐harvesting properties. In this paper, an analytical study of the electron energy loss spectroscopy (EELS) of this kind of metasurfaces is presented. Making use of transformation optics, the response of singular metasurfaces is studied when interacting with a moving electron both in the frequency and time domains. This allows gaining a deeper understanding of the surface plasmon compression at the singularities, which is responsible for the broadband spectra, as well as of the effect of blunt singularities and nonlocality in the metal. Two instances of singular metasurfaces are considered: one with sharp singularities in the form of sharp angle grooves, and one with smooth singularities in the form of two nearly touching surfaces.

Transformation Metamaterials

“…[ 140,141 ] Moreover, this method can be used to study many other plasmonic devices and investigate the associated phenomena, such as nonlocal effects, [ 142–144 ] Casimir interactions, [ 145–147 ] and compact dimensions. [ 148,149 ] The physical idea is shown in Figure 4i,j. [ 150 ] The conformal transformation is chosen as where z = x + iy and z ′ = x ′ + iy ′ are complex numbers denoting virtual space and physical space, respectively; g is an arbitrary constant to adjust the scale of the whole system.…”

“…[140,141] Moreover, this method can be used to study many other plasmonic devices and investigate the associated phenomena, such as nonlocal effects, [142][143][144] Casimir interactions, [145][146][147] and compact dimensions. [148,149] The physical idea is shown in Figure 4i,j. [150] The conformal transformation is chosen as…”

Plasmon localization and giant fields in holographic metasurface for SERS sensors

“…For instance, to calculate the reflection of an electromagnetic wave, the metal grating is replaced by thin plane metal film. The developed method was used to theoretically investigate broadband THz absorption in graphene metasurfaces [50], optical properties of singular metal surfaces [48,51], non-local effects [52], and calculating of the energy loss of an electron flying over the metal modulation [53].…”