Ultra-broadband, high-efficiency, and compact Si crossing.

Area of Science:

• Photonics
• Optical Engineering
• Materials Science

Background:

• Global data traffic growth necessitates advanced broadband and high-density photonic integration solutions.
• Silicon photonics offers CMOS compatibility and scalability but faces challenges in achieving broadband performance for fundamental components like waveguide crossings.

Purpose of the Study:

• To demonstrate a silicon waveguide crossing with efficient broadband operation across the S+C+L bands (1460-1625 nm).
• To achieve significant improvements in bandwidth, insertion loss, and crosstalk compared to existing designs.
• To validate the fabrication robustness and compatibility with commercial silicon photonics processes.

Main Methods:

• Utilized inverse design principles combined with particle swarm optimization and Finite-Difference Time-Domain (FDTD) simulations.
• Designed a compact waveguide crossing with an 8x8 μm² footprint.
• Conducted large-scale experimental validation to confirm performance and fabrication tolerance.

Main Results:

• Achieved an unprecedented 165-nm operational bandwidth, a 175% improvement over previous designs.
• Demonstrated insertion loss below -0.12 dB and crosstalk below -35 dB across the target bands.
• Experimental results showed insertion loss as low as -0.08 dB at 1550 nm, confirming fabrication robustness.

Conclusions:

• The developed silicon waveguide crossing represents a key advance in silicon photonic integration.
• Inverse design is a transformative approach for creating broadband, low-loss, and fabrication-tolerant photonic devices.
• This technology is crucial for enabling next-generation optical interconnects to meet escalating data demands.