Efficient and polarization insensitive edge coupler based on cascaded vertical waveguide tapers.

Area of Science:

• Photonics and Optical Engineering
• Materials Science for Integrated Optics

Background:

• Efficient fiber-to-chip coupling is crucial for photonic integrated circuits (PICs).
• Existing edge couplers often struggle with polarization insensitivity or require complex fabrication processes.

Purpose of the Study:

• To propose and demonstrate an efficient, polarization-insensitive edge coupler (EC).
• To enable low-cost and straightforward implementation for various PIC platforms.

Main Methods:

• Design and fabrication of an edge coupler using two cascaded vertical waveguide tapers.
• Utilized a standard 365 nm (i-line) ultraviolet lithography process.
• Experimental validation on silicon nitride (Si3N4) and thin-film lithium niobate PIC platforms.

Main Results:

• Achieved polarization-insensitive fiber-to-chip coupling efficiency exceeding 70% across the C-band.
• Demonstrated the edge coupler's performance on both Si3N4 and LiNbO3 platforms.
• The fabrication process is compatible with standard i-line lithography.

Conclusions:

• The proposed edge coupler offers an efficient, cost-effective, and easily implementable solution for low-loss chip-fiber coupling.
• This technology can significantly advance the integration of optical components.
• The polarization-insensitive nature simplifies system design and operation.