High-performance tunable resonant electro-optical modulator based on suspended graphene waveguides.

Area of Science:

• Photonics and Plasmonics
• Materials Science
• Electrical Engineering

Background:

• Graphene surface plasmons offer unique tunable waveguiding properties, driving innovation in electro-optical (EO) devices for terahertz (THz) and mid-infrared (MIR) photonic circuits.
• Existing resonance-based modulators often suffer from high losses due to input power interaction with resonant cavities.

Purpose of the Study:

• To propose and numerically investigate a low-loss, highly extinctive resonant electro-optical modulator.
• To leverage suspended graphene plasmonic waveguides for enhanced modulator performance.
• To minimize power loss in the on-state by reducing interaction with the resonance cavity.

Main Methods:

• Numerical investigation using charge transport simulations for steady-state charge distribution.
• Three-dimensional finite-difference time-domain (3D-FDTD) method to analyze guided wave propagation and modulation.
• Analysis of transmission spectrum dependence on geometric parameters and gate voltage tuning.

Main Results:

• Achieved insertion loss (IL) of 1.3 dB and extinction ratio (ER) of 22 dB in a footprint under 3 µm².
• Demonstrated negligible input power interaction with the resonance cavity in the on-state, reducing losses.
• Obtained a modulation bandwidth of 71 GHz with a total capacitance of 4.8 fF.

Conclusions:

• The proposed suspended graphene plasmonic waveguide modulator offers superior performance with low loss and high extinction.
• The device's transmission spectrum is tunable via gate voltage, allowing operation at desired wavelengths.
• The novel structure shows significant potential for applications in MIR and THz integrated circuits, including filters and switches.