Graphene-based hybrid plasmonic waveguide for highly efficient broadband mid-infrared propagation and modulation

Area of Science:

• Photonics and Plasmonics
• Materials Science
• Mid-Infrared (mid-IR) Optics

Background:

• Surface plasmon polaritons (SPPs) are crucial for subwavelength light confinement and manipulation.
• Existing plasmonic waveguides often face limitations in propagation length and mode area.
• Graphene offers tunable optical properties essential for advanced photonic devices.

Purpose of the Study:

• To propose and analyze a novel graphene-based hybrid plasmonic waveguide.
• To achieve highly efficient broadband SPP propagation and modulation in the mid-IR spectrum.
• To enhance light-graphene interaction and SPP confinement using a parabolic-ridged structure.

Main Methods:

• Design of a hybrid plasmonic waveguide incorporating a monolayer graphene sheet, polysilicon gating layer, dielectric buffers, and parabolic-ridged silicon substrates.
• Numerical analysis of SPP propagation length and normalized mode area.
• Investigation of modulation depth by tuning graphene chemical potential across the 10-20 THz frequency range.

Main Results:

• The parabolic-ridged structure significantly increases light-graphene interaction and SPP confinement.
• Achieved long SPP propagation lengths (12.1-16.7 μm) and a small normalized mode area (~10⁻⁴) in the 10-20 THz range.
• Demonstrated modulation depths exceeding 51% across 10-20 THz, reaching nearly 100% above 18 THz.

Conclusions:

• The proposed graphene-based hybrid plasmonic waveguide exhibits excellent broadband mid-IR propagation and modulation performance.
• The parabolic-ridged design offers a substantial improvement in subwavelength confinement compared to non-ridged structures.
• This technology holds promise for developing next-generation mid-IR waveguides, modulators, interconnects, and optoelectronic devices.