30GHz Ge electro-absorption modulator integrated with 3 μm silicon-on-insulator waveguide

Area of Science:

• Photonics and Optical Engineering
• Semiconductor Device Physics
• Integrated Optics

Background:

• High-speed optical modulators are crucial for modern telecommunications.
• Germanium (Ge) offers potential for efficient electro-absorption modulation.
• Integration with silicon photonics platforms is key for scalable optical circuits.

Purpose of the Study:

• To demonstrate a compact, high-speed Ge electro-absorption (EA) modulator.
• To integrate the Ge EA modulator with a silicon-on-isolator (SOI) waveguide.
• To characterize the modulator's performance for high-speed optical communication.

Main Methods:

• Fabrication of a horizontally-oriented p-i-n Ge EA modulator.
• Butt-coupling the Ge modulator with deep-etched and shallow-etched silicon waveguides.
• Adiabatic transition to a single-mode, large-core SOI waveguide.
• Characterization of insertion loss, extinction ratio, and bandwidth.

Main Results:

• Demonstrated a compact device with an active region of 1.0 × 45 µm(2).
• Achieved an extinction ratio of 4-7.5 dB over 1610-1640 nm wavelength range.
• Measured a 3 dB bandwidth exceeding 30 GHz.
• Observed clear eye-diagram openings at 12.5 Gbps, confirming high-speed modulation capability.

Conclusions:

• The integrated Ge EA modulator is suitable for high-speed optical modulation.
• The device exhibits promising performance for next-generation optical interconnects.
• This integration advances the development of compact and efficient silicon photonic devices.