Compact broadband polarization beam splitter using a symmetric directional coupler with sinusoidal bends

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Semiconductor Devices

Background:

• Polarization beam splitters (PBS) are crucial components in optical systems for manipulating light polarization.
• Existing PBS designs often face limitations in terms of size, bandwidth, or performance.
• Silicon-on-insulator (SOI) platforms offer advantages for integrated photonic devices due to their high refractive index contrast and mature fabrication processes.

Purpose of the Study:

• To design and demonstrate a compact broadband polarization beam splitter (PBS).
• To utilize sinusoidal waveguide bends to control polarization mode behavior.
• To achieve efficient separation of transverse-electric (TE) and transverse-magnetic (TM) polarizations on an SOI platform.

Main Methods:

• Design of a symmetric directional coupler incorporating sinusoidal waveguide bends.
• Fabrication of the device on a silicon-on-insulator (SOI) platform.
• Experimental characterization of the PBS performance, including extinction ratio (ER) and polarization isolation (PI), over a broad wavelength range.

Main Results:

• Demonstration of a compact PBS with a nominal coupler length of 8.55 μm.
• Achieved average extinction ratios of 12.0 dB for TE mode and 20.1 dB for TM mode.
• Obtained average polarization isolation of 20.6 dB (through port) and 11.5 dB (cross port).
• The device operated effectively over a bandwidth of 100 nm.

Conclusions:

• The proposed sinusoidal bend design effectively suppresses power exchange for TE modes while enabling efficient TM mode splitting.
• The compact broadband PBS demonstrates high performance metrics suitable for various integrated photonic applications.
• This work contributes a novel approach to polarization management in silicon photonics.