Experimental characterization and analysis of an adjoint method inverse design compact edge coupler solution.

Area of Science:

• Photonics
• Integrated Optics
• Materials Science

Background:

• Edge couplers are crucial for interfacing optical fibers with photonic integrated circuits.
• Traditional edge coupler designs often require a large footprint, limiting device density.
• Silicon nitride is a promising material for photonic integrated circuits due to its low loss and CMOS compatibility.

Purpose of the Study:

• To design and fabricate a compact silicon nitride edge coupler using inverse design.
• To experimentally characterize the coupling performance and loss.
• To analyze the impact of fiber alignment and fabrication variations on performance.

Main Methods:

• Utilized an open-source inverse design framework for component optimization.
• Fabricated the edge coupler using a standard 300 mm foundry lithography process.
• Measured fiber-to-chip coupling loss for quasi-TE and quasi-TM modes at 1550 nm.

Main Results:

• Achieved a compact edge coupler footprint of 12 x 4 µm.
• Measured coupling loss of 5.5 dB for the quasi-TE mode and 2.4 dB for the quasi-TM mode.
• Investigated sensitivity to fiber alignment and fabrication tolerances.

Conclusions:

• Inverse design enables significantly shorter edge couplers compared to adiabatic tapers.
• This compact design enhances integration density in photonic integrated circuits.
• The demonstrated approach is viable for high-performance photonic device fabrication.