Abstract
In this paper, a graphene-based hybrid plasmonic waveguide is proposed for highly efficient broadband surface plasmon polariton (SPP) propagation and modulation at mid-infrared (mid-IR) spectrum. The hybrid plasmonic waveguide is composed of a monolayer graphene sheet in the center, a polysilicon gating layer, and two inner dielectric buffer layers and two outer parabolic-ridged silicon substrates symmetrically placed on both sides of the graphene. Owing to the unique parabolic-ridged waveguide structure, the light-graphene interaction and subwavelength SPPs confinement of the fundamental SPP mode for the hybrid waveguide can be significantly increased. Under the graphene chemical potential of 1.0 eV, the proposed waveguide can achieve outstanding SPP propagation performance with long propagation length of 12.1-16.7 μm and small normalized mode area of ~10-4 in the frequency range of 10-20 THz, exhibiting more than one order smaller in the normalized mode area while remaining the propagation length almost the same level with respect to the hybrid plasmonic waveguide without parabolic ridges. By tuning the graphene chemical potential from 0.1 to 1.0 eV, we demonstrate the waveguide has a modulation depth greater than 51% for the frequency ranging from 10 to 20 THz and reaches a maximum of nearly 100% at the frequency higher than 18 THz. Benefitting from the excellent broadband mid-IR propagation and modulation performance, the graphene-based hybrid plasmonic waveguide may open up a new way for various mid-IR waveguides, modulators, interconnects and optoelectronic devices.
Highlights
Mid-infrared radiation, with the wavelength ranging from 3 μm to 30 μm, has attracted increasing attention in recent years, owing to its extensive exciting applications in imaging, sensing, spectroscopy, and communications [1, 2]
In this study, a graphene-based hybrid plasmonic waveguide with double parabolic-ridged silicon substrates have been demonstrated for highly efficient broadband surface plasmon polariton (SPP) propagation and modulation at mid-IR spectrum
The results show that the fundamental SPP mode is superior to other higher SPP modes with longer propagation length (12.1-16.7 μm) and smaller normalized mode area (~10−4) in the mid-IR frequency between 10 THz and 20 THz under the chemical potential of 1.0 eV
Summary
Mid-infrared radiation, with the wavelength ranging from 3 μm to 30 μm, has attracted increasing attention in recent years, owing to its extensive exciting applications in imaging, sensing, spectroscopy, and communications [1, 2]. Because of supporting surface plasmons in the terahertz and infrared ranges, graphene is considered as one of the most promising SPP materials superior to noble metals with much stronger mode confinement, relatively small propagation loss, especially with a significant advantage of being actively tunable via chemical doping or electrostatic doping [17, 18].
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