Device architectures for low voltage and ultrafast graphene integrated phase modulators.

Area of Science:

• Photonics
• Materials Science
• Electrical Engineering

Background:

• Graphene's unique atomic structure and electronic properties offer potential for advanced photonic devices.
• Fermi-level tunability in graphene enables its use as an active layer in electro-optic modulation.
• Graphene's low-loss metallic characteristics allow for proximity to active layers, facilitating low-voltage operation.

Purpose of the Study:

• To investigate hybrid device architectures leveraging graphene's semiconductor and metallic properties.
• To develop ultrafast and energy-efficient electro-optic phase modulators.
• To explore applications on both semiconductor and dielectric platforms.

Main Methods:

• Investigated directly contacted graphene-silicon heterojunctions with doped silicon electrodes.
• Simulated graphene-integrated lithium niobate modulators with graphene as a transparent electrode.
• Analyzed carrier modulation, transit times, RC constants, and electro-optic field overlap.

Main Results:

• Graphene-silicon heterojunctions demonstrated ultrafast modulation (67 GHz bandwidth) and a Vπ·L of 1.19 V·mm.
• Graphene-lithium niobate modulators showed a 2.5× improvement in electro-optic field overlap and a Vπ of 0.2 V.
• Minimal additional loss (4.6 dB/cm) was observed in graphene-integrated lithium niobate waveguides.

Conclusions:

• Hybrid device architectures utilizing graphene offer significant performance improvements for electro-optic modulators.
• Graphene's properties enable ultrafast modulation speeds and energy efficiency.
• These findings pave the way for next-generation integrated photonic devices.