A compact silicon grating coupler based on hollow tapered spot-size converter

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Nanophotonics

Background:

• Efficient fiber-to-chip coupling is crucial for photonic integrated circuits (PICs).
• Traditional couplers often require significant footprint and complex fabrication.
• Miniaturization of optical components is a key challenge in modern photonics.

Purpose of the Study:

• To propose and demonstrate a new compact silicon grating coupler.
• To achieve efficient light coupling from optical fibers to silicon chips with a minimized taper length.
• To reduce the physical footprint of coupling components in PICs.

Main Methods:

• Design of a silicon grating coupler incorporating a hollow tapered waveguide.
• Characterization of optical mode spot-size conversion from micro- to nano-scales.
• Evaluation of coupling efficiency and 3-dB coupling bandwidth.
• Fabrication and integration into a photonic integrated circuit.

Main Results:

• The proposed coupler reduces lateral dimension from 15 µm to 300 nm over a 60 µm length.
• Achieved a compact physical footprint of 81 µm × 15 µm.
• Demonstrated high coupling efficiency of 72%.
• Obtained a wide 3-dB coupling bandwidth of 69 nm.

Conclusions:

• The novel hollow tapered waveguide grating coupler offers a compact and efficient solution for fiber-to-chip integration.
• This design significantly reduces the footprint of PICs while maintaining high performance.
• The demonstrated performance metrics are promising for advanced photonic applications.