Compact dual-mode waveguide crossing based on adjoint shape optimization.

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Materials Science (Silicon-on-Insulator)

Background:

• Waveguide crossings are essential components in integrated photonic circuits for signal routing.
• Existing designs often face challenges with performance trade-offs, such as insertion loss and crosstalk.
• Dual-mode operation in waveguides allows for increased functionality within a smaller footprint.

Purpose of the Study:

• To design, fabricate, and characterize a high-performance, compact dual-mode waveguide crossing.
• To leverage adjoint shape optimization for efficient design of photonic devices.
• To demonstrate low insertion loss and crosstalk for both TE0 and TE1 modes.

Main Methods:

• Adjoint shape optimization algorithm for computationally efficient design.
• Fabrication on a silicon-on-insulator (SOI) platform.
• Experimental characterization of insertion loss and crosstalk at 1550 nm.

Main Results:

• Achieved insertion losses of 0.83 dB for TE0 and 0.50 dB for TE1 modes at 1550 nm.
• Demonstrated crosstalk below -20 dB for both modes across an 80 nm wavelength range.
• Fabricated a compact device with a footprint of only 5x5 μm².

Conclusions:

• The adjoint-method-based optimization is effective for designing high-performance photonic devices.
• The developed dual-mode waveguide crossing meets key performance metrics for integrated photonics.
• The compact size and excellent performance make this device suitable for advanced optical circuits.