Green formulation for studying electromagnetic scattering from graphene--coated wires of arbitrary section

CLAUDIO VALENCIA; MAXIMO RISO; MAURO CUEVAS; RICARDO A. DEPINE

JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS

OPTICAL SOC AMER

Lugar: Washington; Año: 2017

0740-3224

We present a rigorous electromagnetic method based on Green?s second identity for studying theplasmonic response of graphene?coated wires of arbitrary shape. The wire is illuminated perpendicularto its axis by a monochromatic electromagnetic wave and the wire substrate is homogeneous and isotropic.The field is expressed everywhere in terms of two unknown source functions evaluated on the graphenecoating which can be obtained from the numerical solution of a coupled pair of inhomogeneous integralequations. To assess the validity of the Green formulation, the scattering and absorption efficienciesobtained numerically in the particular case of circular wires are compared with those obtained fromthe multipolar Mie theory. An excellent agreement is observed in this particular case, both for metallicand dielectric substrates. To explore the effects that the break of the rotational symmetry of the wiresection introduces in the plasmonic features of the scattering and absorption response, the Greenformulation is applied to the case of graphene-coated wires of elliptical section. As might be expectedfrom symmetry arguments, we find a two-dimensional anisotropy in the angular optical response of thewire, particularly evident in the frequency splitting of multipolar plasmonic resonances. The comparisonbetween the spectral position of the enhancements in the scattering and absorption efficiency spectra forlow?eccentricity elliptical and circular wires allows us to guess the multipolar order of each plasmonicresonance. We present calculations of the near field distribution for different frequencies which explicitlyreveal the multipolar order of the plasmonic resonances. They also confirm the previous guess and serveas a further test on the validity of the Green formulation.