Reducing metal-induced optical loss in graphene-on-silicon-nitride electro-absorption modulators

Area of Science:

• Photonics
• Materials Science
• Electrical Engineering

Background:

• Metal-induced absorption in graphene-on-silicon-nitride (Si3N4) modulators limits performance.
• Evanescent coupling to metallic gate electrodes causes optical loss near the waveguide core.

Purpose of the Study:

• To systematically investigate the impact of electrode geometry and proximity on modulator performance.
• To reduce metal-induced optical loss in dual-layer graphene modulators on a Si3N4 platform.

Main Methods:

• Utilized three-dimensional electromagnetic simulations.
• Conducted experimental measurements on fabricated modulators.
• Compared continuous bar electrodes with segmented via-type contacts.

Main Results:

• Reduced metal-induced attenuation from 0.36 dB/µm to 0.09 dB/µm.
• Maintained graphene absorption at approximately 0.16 dB/µm.
• Achieved a modulation slope of ~1 dB/V at 1.31 µm with optimized via contacts.

Conclusions:

• Segmented via-type contacts effectively minimize metal-induced optical loss.
• Established design rules for electrode geometry and spacing to reduce optical loss.
• Provides a pathway for developing advanced CMOS-compatible graphene modulators with lower loss for integrated photonics.