High-efficiency wideband SiN_x-on-SOI grating coupler with low fabrication complexity

Area of Science:

• Integrated photonics
• Nanophotonics
• Materials science

Background:

• Chip-fiber grating couplers are essential for integrated photonics, enabling on-wafer testing and packaging.
• Silicon nitride (SiNx) grating couplers offer wider bandwidths than silicon but have lower efficiency due to a lower refractive index.
• Existing methods to enhance SiNx coupler efficiency, like using silicon grating reflectors, involve complex, multi-step fabrication processes.

Purpose of the Study:

• To demonstrate a simplified fabrication process for high-performance SiNx-on-SOI grating couplers.
• To achieve efficient light coupling between optical fibers and integrated photonic circuits using a novel SiNx grating design.
• To reduce fabrication complexity and cost for integrated photonic devices.

Main Methods:

• Fabrication of a SiNx-on-SOI grating coupler using a single patterning step for the grating.
• Design and implementation of a transverse-electric (TE) mode grating coupler.
• Experimental characterization of the coupler's performance, including coupling coefficient and 1-dB bandwidth.

Main Results:

• Achieved a coupling coefficient of -2.5 dB.
• Measured a 1-dB bandwidth of 65 nm.
• Demonstrated a simplified fabrication process requiring only one patterning step, eliminating the need for high precision alignment (HPA) and chemical mechanical polishing (CMP).

Conclusions:

• The developed SiNx-on-SOI grating coupler offers a practical and efficient solution for integrated photonics.
• The simplified fabrication process significantly reduces manufacturing complexity and cost.
• This approach paves the way for more accessible and scalable integrated photonic devices.