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The lower and sub-THz frequency range: the optimal spectrum for coupled graphene-metal like plasmon polaritons Host Publication: the International Conference on Semiconductor Mid-IR Materials and Optics SMMO2014 Authors: J. Stiens, H. Alkorre, G. Shkerdin and R. Vounckx Publication Year: 2014
Abstract: The properties of graphene plasmons and plasmon-polaritons supported by structures containing one or more graphene layers have already been investigated [1]. However, the coupling of such graphene plasmon-polaritons with another type of the structural eigenmodes (surface metal-plasmon polaritons or waveguide modes) has not been thoroughly examined [2], for sure not in the lower and sub-THz range with an important intraband contribution in the optical surface conductivity [3]). We will discuss the various solutions of the dispersion equation of TM coupled modes in a 4-layer structure comprising a metal substrate, a dielectric buffer, a graphene mono-layer and air. We will show that for Fermi energy levels smaller than a critical value, the metal and graphene modes exhibit only distortions with respect to their uncoupled behaviour. For Fermi energy levels larger than this critical value, the metal-like polariton spectrum splits up in two branches: a first modified metal-like polariton branch exists within the whole range of buffer layer thicknesses a second branch, called cutoff metal-like polariton branch, exists only within a limited range of buffer thicknesses and featuring Brewster type characteristics at cutoff. We will discuss how the coupling behavior between graphene and metal modes depends on frequency and the Fermi level in graphene.
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