Abstract
Being one-atom thick and tunable simultaneously, graphene plays the revolutionizing role in many areas. The focus of this paper is to investigate the modal characteristics of surface waves in structures with graphene in the far-infrared (far-IR) region. We discuss the effects exerted by substrate permittivity on propagation and localization characteristics of surface-plasmon-polaritons (SPPs) in single-layer graphene and theoretically investigate characteristics of the hybridized surface-phonon-plasmon-polaritons (SPPPs) in graphene/LiF/glass heterostructures. First, it is shown how high permittivity of substrate may improve characteristics of graphene SPPs. Next, the possibility of optimization for surface-phonon-polaritons (SPhPs) in waveguides based on LiF, a polar dielectric with a wide polaritonic gap (Reststrahlen band) and a wide range of permittivity variation, is demonstrated. Combining graphene and LiF in one heterostructure allows to keep the advantages of both, yielding tunable hybridized SPPPs which can be either forwardly or backwardly propagating. Owing to high permittivity of LiF below the gap, an almost 3.2-fold enhancement in the figure of merit (FoM), ratio of normalized propagation length to localization length of the modes, can be obtained for SPPPs at 5–9 THz, as compared with SPPs of graphene on conventional glass substrate. The enhancement is efficiently tunable by varying the chemical potential of graphene. SPPPs with characteristics which strongly differ inside and around the polaritonic gap are found.
Highlights
After the rise of graphene, the two-dimensional periodic array of carbon atoms arranged in a honeycomb lattice[1,2], a great deal of attention has been attracted to its potential applications in optoelectronics[3] and plasmonics[4]
In order to investigate influence of substrate on surface plasmon polariton (SPP) of a single-layer graphene, we numerically study the basic effects of variation of permittivity of a lossless, dispersion-free dielectric substrate, εd, on the SPPs characteristics, i.e., propagation length, localization length, and figure of merit
From the investigation of graphene SPPs for different dispersion-free dielectric substrates, it has been understood that the use of lossless high-permittivity substrates allows us to considerably increase figure of merit (FoM) of the structure
Summary
After the rise of graphene, the two-dimensional periodic array of carbon atoms arranged in a honeycomb lattice[1,2], a great deal of attention has been attracted to its potential applications in optoelectronics[3] and plasmonics[4]. Alongside the noble metals and graphene, polar dielectrics offer simultaneous sub-diffractional confinement, low optical losses, and operation in the mid-IR to THz spectral ranges through the stimulation of surface phonon polariton (SPhP) modes[29]. Recent experimental and theoretical studies on graphene on SiO228,40,41 and SiC42–44 substrates have shown that the graphene dispersion relation in the mid-IR range can be significantly modified due to the substrate phonons with extra modes arising due to plasmon-phonon coupling This coupling has been considered as surface-phonon-plasmon-polaritons, or SPPPs28. We theoretically investigate the far-IR propagation and localization characteristics of SPPs of a single-layer graphene on dispersion-free dielectric substrates and SPPPs supported by the single-layer graphene on a thin film of LiF, a polar dielectric. To the best of our knowledge, the results presented in this paper is the first attempt to systematically study the effects of dispersion-free and dispersive polar substrates on graphene surface plasmons characteristics at the far-IR region
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
