Polarization rotation Bragg grating using Si wire waveguide with non-vertical sidewall.

Area of Science:

• Photonics
• Optical Engineering
• Materials Science

Background:

• Bragg gratings are widely used as wavelength filters in optical systems.
• Polarization sensitivity in optical filters can limit their performance and applicability.
• Achieving polarization independence is a key challenge in optical filter design.

Purpose of the Study:

• To design and demonstrate a polarization independent Bragg grating wavelength filter.
• To utilize polarization rotation to achieve identical filter characteristics for orthogonal input polarizations.
• To overcome the limitations of polarization-dependent optical filters.

Main Methods:

• Employing a non-vertical waveguide sidewall design.
• Implementing an antisymmetric grating structure to induce polarization rotation.
• Utilizing optical simulations to verify the proposed concept.
• Conducting experimental validation of the designed filter.

Main Results:

• Successfully generated polarization rotation of fundamental modes.
• Achieved identical diffraction efficiencies and peak wavelengths for two orthogonal input polarizations.
• Demonstrated the polarization independent operation of the Bragg grating filter.
• Validated the concept through both simulation and experimental results.

Conclusions:

• The proposed method effectively creates polarization independent Bragg grating wavelength filters.
• Non-vertical waveguide sidewalls and antisymmetric gratings are viable for polarization rotation.
• This approach offers a promising solution for polarization-sensitive optical applications.