Ultracompact electro-optic waveguide modulator based on a graphene-covered λ/1000 plasmonic nanogap

Area of Science:

• Optoelectronics
• Nanophotonics
• Graphene technology

Background:

• Graphene plasmons offer extreme field confinement and electro-optic tunability for compact waveguide modulators.
• Miniaturization of graphene plasmon modulators is limited by plasmon wavelength and graphene material loss.
• Existing devices are constrained by the diffraction limit and performance bounds.

Purpose of the Study:

• To overcome miniaturization and performance limitations in graphene-based waveguide modulators.
• To propose a novel device architecture for enhanced modulator performance.
• To enable practical applications of graphene modulators with improved robustness.

Main Methods:

• Utilized a graphene-covered plasmonic nanogap waveguide with light concentrated at sub-wavelength scales (λ/1000).
• Employed a modulation mechanism based on interference between non-resonant background transmission and gate-tunable nanogap mode.
• Investigated device performance with a focus on modulation depth and robustness against low carrier mobility.

Main Results:

• Achieved modulation depths exceeding 20 dB.
• Concentrated light on length scales significantly smaller than the graphene plasmon wavelength.
• Demonstrated robust switching behavior even with low graphene carrier mobility (1000 cm²/Vs).

Conclusions:

• The proposed plasmonic nanogap waveguide effectively overcomes limitations of graphene plasmon resonances for compact modulators.
• The device offers significant miniaturization potential and high modulation performance.
• The robustness against low carrier mobility makes the technology suitable for practical optoelectronic applications.