High-Efficiency Plasmonic Third-Harmonic Generation with Graphene on a Silicon Diffractive Grating in Mid-infrared...

Area of Science:

• Photonics
• Materials Science
• Nanoscience

Background:

• Graphene exhibits high third-order nonlinear susceptibility, ideal for enhancing plasmonic third-harmonic generation (THG).
• Existing configurations struggle to simultaneously excite fundamental frequency (FF) graphene plasmons (GPs) and guide generated third-harmonic frequency (THF) GPs.
• Graphene plasmons offer potential for efficient nonlinear optical processes in the infrared spectrum.

Purpose of the Study:

• To propose and numerically demonstrate an effective configuration for enhanced THG using graphene plasmons.
• To achieve efficient excitation and guiding of both FF and THF GPs.
• To explore graphene-based light sources for mid- and far-infrared silicon photonics.

Main Methods:

• Utilizing a diffractive silicon grating underneath a graphene sheet to excite FF GPs via guided-mode resonance.
• Leveraging the enhanced field intensity of FF GPs for efficient conversion to THF GPs.
• Simulating the generation and guiding of THF GPs along connected low-loss GP waveguides.

Main Results:

• Achieved a large THG conversion efficiency of 3.68 × 10^-7 at an incident power density of 0.19 MW/cm² at 28.62 μm.
• Demonstrated efficient excitation of FF GPs using normal-incidence plane wave illumination.
• Showcased the capability to guide generated THF GPs along integrated waveguides.

Conclusions:

• The proposed diffractive silicon grating configuration effectively enhances graphene plasmon-based THG.
• This approach enables simultaneous generation and guiding of THF GPs, overcoming previous limitations.
• The findings pave the way for developing novel graphene-based light sources for mid- and far-infrared silicon photonic integrated circuits.