Silicon waveguide grating coupler for perfectly vertical fiber based on a tilted membrane structure.

Area of Science:

• Photonics and optical engineering
• Integrated optics
• Semiconductor device fabrication

Background:

• Efficient interfacing between silicon-on-insulator (SOI) waveguides and optical fibers is crucial for integrated photonic circuits.
• Conventional grating couplers typically require oblique fiber alignment, limiting integration density and manufacturing processes.
• Vertical fiber interfacing offers advantages for compact device design and automated assembly.

Purpose of the Study:

• To demonstrate a grating coupler for vertical interfacing between SOI waveguides and single-mode fibers.
• To evaluate the performance metrics including coupling efficiency, bandwidth, and back reflection.
• To ensure compatibility with existing mass production techniques for grating couplers.

Main Methods:

• Design and fabrication of a grating coupler utilizing a tilted membrane structure.
• Experimental characterization of the grating coupler's performance for transverse-electric (TE) polarized light.
• Analysis of coupling efficiency, 1 dB bandwidth, and back reflection in the SOI waveguide.

Main Results:

• Achieved a peak coupling efficiency of 28.5% for TE polarized light.
• Obtained a 1 dB bandwidth of 38 nm.
• Estimated back reflection in the SOI waveguide to be 1.4%.

Conclusions:

• The demonstrated grating coupler enables efficient vertical fiber coupling to SOI waveguides.
• The performance metrics are comparable to conventional grating couplers used for oblique fiber alignment.
• The proposed design is compatible with mass production, facilitating practical applications in integrated photonics.