Polarization-insensitive silicon waveguide crossing based on multimode interference couplers.

Area of Science:

• Photonics
• Integrated Optics
• Semiconductor Devices

Background:

• Waveguide crossings are essential components in integrated photonic circuits.
• Achieving polarization-insensitivity and miniaturization in crossings remains a challenge.
• Silicon-on-insulator (SOI) technology offers high refractive index contrast for compact devices.

Purpose of the Study:

• To propose and demonstrate a novel polarization-insensitive waveguide crossing.
• To achieve a compact footprint for the device.
• To ensure low insertion loss and crosstalk for practical applications.

Main Methods:

• Design and simulation of a waveguide crossing utilizing two orthogonal multimode interference (MMI) couplers.
• Fabrication on a silicon-on-insulator (SOI) platform using a single fully etched step.
• Experimental characterization of insertion loss and crosstalk across the 1520-1610 nm wavelength band for both transverse-electric (TE) and transverse-magnetic (TM) polarizations.

Main Results:

• Demonstration of a polarization-insensitive waveguide crossing with a compact footprint of approximately 23 μm × 23 μm.
• Achieved low insertion losses for both TE and TM polarizations.
• Exhibited low crosstalk levels for both polarizations over the specified wavelength range.

Conclusions:

• The proposed MMI-based waveguide crossing is a viable solution for polarization-insensitive routing in integrated photonic circuits.
• The device's compact size and simple fabrication process make it attractive for scalable photonic integration.
• The demonstrated performance metrics indicate suitability for various photonic applications requiring efficient light manipulation.