Mode-evolution-based coupler for high saturation power Ge-on-Si photodetectors

Area of Science:

• Photonics
• Optoelectronics
• Materials Science

Background:

• Germanium-on-silicon (GeSi) photodetectors are crucial for integrated photonics.
• High input powers can cause saturation effects like carrier screening, limiting detector performance.
• Conventional coupling methods struggle with efficient light delivery to the germanium region.

Purpose of the Study:

• To introduce a novel mode-evolution-based coupler for GeSi photodetectors.
• To enhance high saturation power performance by ensuring uniform illumination of the germanium region.
• To overcome limitations of existing detectors under high optical power.

Main Methods:

• Design and fabrication of a mode-evolution-based coupler.
• Integration of the coupler with germanium-on-silicon photodetectors.
• Characterization of photocurrent generation and opto-electrical bandwidth under high-power illumination.

Main Results:

• Demonstrated uniform illumination of the intrinsic germanium region, reducing saturation effects.
• Achieved 70% higher photocurrent generation (9.1–15.5 mA) compared to conventional detectors.
• Obtained over 40 times higher opto-electrical bandwidth (0.7–31 GHz) under high-power conditions.

Conclusions:

• The mode-evolution coupler significantly enhances the high-power and high-speed performance of GeSi photodetectors.
• The compact nature of the coupling method is advantageous for integrated systems.
• This technology opens new avenues for advanced applications in silicon photonics.