Abstract
The waveguiding of terahertz surface plasmons by a GaAs strip-loaded graphene waveguide is investigated based on the effective-index method and the finite element method. Modal properties of the effective mode index, modal loss, and cut-off characteristics of higher order modes are investigated. By modulating the Fermi level, the modal properties of the fundamental mode could be adjusted. The accuracy of the effective-index method is verified by a comparison between the analytical results and numerical simulations. Besides the modal properties, the crosstalk between the adjacent waveguides, which determines the device integration density, is studied. The findings show that the effective-index method is highly valid for analyzing dielectric-loaded graphene plasmon waveguides in the terahertz region and may have potential applications in subwavelength tunable integrated photonic devices.
Highlights
The terahertz (THz) wave, usually defined as a frequency ranging from 1 to 10 THz, has attracted numerous research interests due to its potential applications in the fields of spectroscopy, imaging, defense industries, on-chip communications [1,2,3,4,5,6], etc
Our findings show that the effective-index method (EIM) is highly valid for analyzing dielectric-loaded graphene surface plasmon waveguides (DLGSPWG) in the THz region, and the results are verified by the numerical simulations based on the finite element method (FEM)
We extend concept dielectric-loaded plasmon waveguide from nearand mid-infrared band to the modes of the are studied by mid-infrared band to the THz band
Summary
The terahertz (THz) wave, usually defined as a frequency ranging from 1 to 10 THz, has attracted numerous research interests due to its potential applications in the fields of spectroscopy, imaging, defense industries, on-chip communications [1,2,3,4,5,6], etc. By using THz waveguides, THz waves can be concentrated in the subwavelength region, offering a tightly confined modal field beyond the diffraction limit [7]. Compared with the metallic waveguides, graphene plasmon waveguides could confine the infrared waves into the deep subwavelength scale, and the guided modes could be tuned [34]. In the THz band, Huang et al [49] proposed a graphene-coated nanowire with a drop-shaped cross section to realize low loss waveguiding with an ultra-strong mode confinement. Zhou et al [51] proposed a graphene-based hybrid plasmonic waveguide to achieve ultra-deep subwavelength modal field confinement. To the best of our knowledge, the modal properties and crosstalk in dielectric-loaded graphene surface plasmon waveguides (DLGSPWG) have not yet been fully investigated in the THz region. The results show that the electromagnetic field in the corner regions is only partly responsible for the difference between the EIM and FEM results and that the crosstalk between adjacent structures is negligible even at a very small separation distance
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