Compact high-efficiency perfectly-vertical grating coupler on silicon at O-band

Area of Science:

• Photonics
• Optical Engineering
• Materials Science

Background:

• Efficient interfacing between silicon waveguides and optical fibers is crucial for silicon photonics.
• Minimizing back reflections is essential for device performance and stability.

Purpose of the Study:

• To demonstrate a compact, high-efficiency grating coupler for O-band operation.
• To achieve efficient coupling between silicon waveguides and vertical fibers with minimal reflections.

Main Methods:

• Utilizing a tilted silicon membrane to reduce reflections.
• Employing circular grating lines to shorten device length.
• Investigating fabrication processes and membrane stability.

Main Results:

• Achieved a peak coupling efficiency of 57%.
• Obtained a 1-dB coupling bandwidth greater than 28nm.
• Theoretically estimated back reflections to be as low as 1%.

Conclusions:

• The developed grating coupler is compact, efficient, and compatible with standard silicon photonic fabrication.
• The tilted membrane and circular grating design effectively minimize reflections and device footprint.
• This technology facilitates robust fiber-to-chip integration for photonic integrated circuits.