Polarization splitting directional coupler using tilted subwavelength gratings.

Area of Science:

• Photonics
• Integrated Optics
• Nanophotonics

Background:

• On-chip polarization splitters are crucial for coherent optical communication and polarization diversity circuits.
• Existing devices often rely on asymmetric directional couplers, necessitating complex fabrication processes like additional material layers or etch steps.

Purpose of the Study:

• To demonstrate a polarization splitter utilizing a directional coupler with fully etched subwavelength waveguides.
• To achieve polarization splitting by varying only the tilt angle of silicon segments within the waveguides.

Main Methods:

• Design and fabrication of a directional coupler using two subwavelength waveguides.
• Engineering the tilt angle of silicon segments in each waveguide to induce asymmetry.
• Characterization of the device's performance, including insertion loss, extinction ratio, and bandwidth.

Main Results:

• The developed polarization splitter operates with deep-UV compatible feature sizes.
• The device measures only 14 µm in length.
• It achieves insertion losses below 1 dB and an extinction ratio exceeding 15 dB over a 72 nm bandwidth.

Conclusions:

• The proposed method offers a simplified fabrication approach for polarization splitters.
• The device's compact size and performance metrics make it suitable for advanced optical communication systems.
• Varying waveguide segment tilt angles is an effective strategy for on-chip polarization manipulation.