Broadband and low-loss TM-pass polarizer using tilted subwavelength structures

Area of Science:

• Photonics
• Materials Science
• Electrical Engineering

Background:

• Silicon-on-Insulator (SOI) platforms are widely used in photonics.
• Strong birefringence in SOI necessitates single-polarization operation for many applications.
• On-chip polarizers are essential for suppressing unwanted polarization states in SOI systems.

Purpose of the Study:

• To design and propose a novel TM-pass polarizer for the standard 220 nm SOI platform.
• To achieve broadband operation with low insertion loss and high extinction ratio.
• To overcome design challenges related to differential modal confinement of TE and TM polarizations in SOI.

Main Methods:

• Engineering a Bragg grating with a subwavelength metamaterial structure.
• Utilizing the grating to reflect the fundamental TE mode into the first-order TE mode.
• Simultaneously allowing the TM mode to pass through the device with minimal loss.

Main Results:

• Demonstrated a TM-pass polarizer with an extinction ratio exceeding 20 dB.
• Achieved insertion losses below 0.5 dB for the TM mode.
• Obtained back-reflections of the fundamental TE mode below -20 dB.
• Validated performance over a 150 nm bandwidth using 3D-FDTD simulations.

Conclusions:

• The proposed Bragg grating polarizer offers a viable solution for TM-pass filtering in SOI photonic circuits.
• The design effectively suppresses TE polarization while minimally impacting TM polarization.
• This advancement is critical for enabling high-performance photonic integrated circuits operating with a single polarization.